▲ 



1 ft c 



■Hi 






«>*?#Jifi 



/..y^ 







Class TK65.5Q 

Book 7D 1 

Copyright N° 

COPYRIGHT DEPOSIT. 




Copyright, Underwood & Underwood, N. Y. 
LOFTY AERIALS OF A POWERFUL RADIO BROADCASTING 

STATION 
Photo shows one of the two aerial towers, 183 feet high, mounted 
on a five-story building of the Schenectady (N.Y.) works of The General 
Electric Company, which supports the antennae. Daily they send forth 
programs to the thousands of radio fans in Eastern America. 

Note the two steeplejacks at top of tower and compare sizes. 




Copyright, Underwood & Underwood, N. Y. 
SHE SINGS 100,000 CHILDREN TO SLEEP EVERY NIGHT 
Have you listened to sweet lullabies that come floating over the 
radio? If hot, you are missing something. Almost every night she sends 
out her lullaby music over The Westinghouse Electric Company's radio 
at Chicago. Photo shows Miss Forster s inging for her audience of a 
hundred thousand. 



RADIO 

Miracle of the 20™ Century 

BEING 

A Vivid, Authentic and Intensely Interesting Story of 

Radio Communication and the Remarkable 

Accomplishments of Men Who Have 

Made It Possible to Talk 

Through Space To 

People Miles 

Away 

A Story of Human Achievement That 
Stands Unrivalled in the His- 
tory of Humanity 

TOGETHER WITH 

A Colorful Portrayal, Giving a Broad, General View of the Whole 

Subject of Wireless Telegraph and Telephone and 

Its Marvelous Development 

By the nvell-knoivn Authors and Editors 

FREDERICK E. DRINKER JAMES G. LEWIS, M. E. 

Profusely Embellished With 

Half-tone Illustrations From Photographs, Pen and Ink Drawings, 
Diagrams, Etc., Made Expressly for the Book, Showing Phases of 
Construction and Visualizing Essential Details. 






"K K 



L*jf 



Entered according to Act of Congress, in the year 1922, by 

National Publishing Co., in the Office of the Librarian 

of Congress, at Washington, D. C. 



Z3-tf1 1 1 



. M 28 i922 

(g)CI.At>77335 



PREFACE 

IN presenting this volume for public consideration the 
editors have endeavored to provide the average reader 
with a vivid picture of the vast realities and possibili- 
ties of the marvelous radio as they have and may in the 
future affect all men in their daily lives; and to trace 
inception and growth of wireless communication through 
the fields of science and mechanics to a brilliant climax 
which has cast a halo / around the heads of a dozen men 
and sent its rays far out into the world. 

No attempt has been made to compile a highly technical 
or scientific volume dealing with electricity and radio 
communication or to provide a textbook on the subject, 
but to give in as interesting and simple way as possible a 
measure of understandable information that will help 
anyone answer in a general way the questions which every 
uninitiated person asks: "What is radio !" "How does 
the lecture or music come through space without wires to 
carry it?" "Why could I never hear the sound waves 
before ? ' ' and ' ' Who discovered radio ? ' ' 

Nothing that has been given to the world by science in 
a century can compare with the radio in the range of pos- 
sibilities that it opens to man, and no imagination can 
conceive of the influence it may have upon our lives and 
the future of the world. A new use and a new application 
of the principle is being developed almost daily. Its popu- 
larity is growing by leaps and bounds. Nothing but the 
limit of man's genius seems to restrict the field to which, 
it may not in some way be applied. 

In the complicated scheme of civilization it may serve 
as a protector of human life, a companion of the pioneer, 



PREFACE 

an aid to education, a world-wide entertainer and per- 
haps a means of communication through which other 
worlds may be reached. The more you learn about it 
the more marvelous it seems, and so the editors have 
tried to convey to you this impression of bigness, of 
power, of unlimited scope with which the radio seems to 
be invested in a way that will prove entertaining and 
reward you for having perused its pages. 

The Editors. 



CONTENTS 

PAGE 



Preface 



CHAPTER I. 

Romance and Marvel of the Wireless — Radio the Sensation of 
the Age — Most Spectacular Electrical Development in all 
History — A New World of Science 17 

CHAPTER II. 

Simple Facts about Radio — Equipment — Transmitting and Re- 
ceiving — Functions of Various Parts — Commonplace Defini- 
tions — Antenna, Receiver, Detectors 24 

CHAPTER III. 

The Wireless Machine — The Telegraph and Telephone — A Mil- 
lion Users in a Year — The Medium of Universal Communi- 
cation — Useful and Amusement Providing 32 

CHAPTER IV. 

Effects and Influence of Wireless Communication on Civilization 
— International Relations — Educational Possibilities — Fu- 
ture Developments 42 

CHAPTER V. 

Scientists and Wizards Who Helped Develop the Wireless — 
Marconi — Edison — Fleming — DeForest — Squier — Poulsen — 
Alexanderson — Steinmetz 51 

CHAPTER VI. 

Sound Waves — Amplifiers — Condensers — The Vacuum Tube and 

the Part It Plays — Alternating and Direct Impulses 63 

5 



6 CONTENTS 

CHAPTER VII. PAGE 

Electricity — What Is It? — Electrons — Atoms — Matter and Its 
Component Parts — The Valve Theory — What Has Made 
Wireless Telephony Possible ? 68 

CHAPTER VIII. 

What Air Really Is — Atmospheric Pressure and How It Was 
Discovered — Three Forms of Matter — Molecular Attraction 
— How Big Is a Molecule? — Moisture in the Air — Measure 
of Humidity 77 

CHAPTER IX. 

Radiation — Radiant Energy — Intensity of Radiation — Reflection 
— Refraction — Diathermancy — Obscure Rays — Absorption — 
Radiation and Absorption — Distribution of Radiant Energy 86 

CHAPTER X. 

Heat Waves — Conduction — Convection — Wave Motions — Har- 
monic Waves — Interference of Waves — Medium Necessary to 
Transmission of Waves — The Ether the Medium for Radio 
Waves 95 

CHAPTER XL 

Magnetism — Lodestone — The Compass — Hard and Soft Iron — 
Effect on Nickel, Silver, Gold — How to Make a Magnet — 
— Magnetic Fields 105 

CHAPTER XII. 

What Is Electricity ? — The Amber Rod — Glass Rod — Sealing- Wax 
Rod — Vitreous and Resinous Electricity — Laws of Attrac- 
tion and Repulsion — The Proof Plane — The Electroscope . . 117 

CHAPTER XIII. 

Electrical Machines — Newton, Hawksbee, Ramsden, Von Guericke 
— Wimshurst Machine — Leyden Jar — Strain in the Air — 
Can Electricity Pass Through Glass? 127 



CONTENTS 7 

CHAPTER XIV. P AGE 

Franklin and His Famous Experiment — What Is Lightning? — 
Effect of Atmospheric Change on Electrical Conditions — 
Electro-magnetism in Wires, Coils and Spirals — Effects of 
Thunderstorms — First Use of Wires for Telegraphic Trans- 
mission — The Wire Eliminated 136 

CHAPTER XV. 

How We Hear Sounds — Sounds Exist Only Where There Is 
Someone to Hear Them — The Telephone Transmitter and 
Receiver — In Radio Vibrations Are Reduced to Bring Them 
Within the Scope of the Human Ear 144 

CHAPTER XVI. 

How to Make a Simple Receiving Set — Aerials — Details of Con- 
struction — Great Fun Receiving 151 

CHAPTER XVII. 

Radio in the World War — Radio Control and Direction of Ships 

at Sea — Airplanes Directed from Land 165 

CHAPTER XVIII. 

Radio Regulation — Government Control in Peace and War — 
Rules 172 

CHAPTER XIX. 

Radio as an Agent of Mercy and the Protector of Man — Heroes 

of the Wireless — The Titanic and Carpathian 182 

CHAPTER XX. 

Eroadcasting — How It x\ffected the Development of Radio — 
Big Electrical Company Pioneers in the Field — Colleges — 
Telephone Companies and Amateurs 18 D 

CHAPTER XXI. 

The Theory of Radio — Basic Principles Explained with Dia- 
grams — Transmitter — Aerial — Tuning — Receiving Set — De- 
tector — Vacuum Tube 196 



v 



CONTENTS 

CHAPTER XXII. PAGE 

Hook-ups an Interesting Study — Same Principles Involved in 

All — Amplification and Refinements 207 

CHAPTER XXIII. 

Vacuum Tube Detector Set Next Step of Progress in the Build- 
ing of a Radio Set — Back to Simple Principles of Radio 
Communication 217 

CHAPTER XXIV. 

How to Change Inductance and Capacity Energizing an Induct- 
ance — Capacity Circuit — The Potential — A Simple Trans- 
mitting System 230 

CHAPTER XXV. 

A Typical Spark Transmitting Circuit — Spark Gaps — Oscillation 

Transformers and Coupling — Tuning of a Circuit — Damping 247 

CHAPTER XXVI. 

Other Methods of Coupling — Why Tuned Circuits Are Necessary 

— Resistance — Interference 263 

CHAPTER XXVII. 

Now We Come to Vacuum Tube — Electric Action — The Batteries 
— Grid Action — Vacuum Tube as a Detector — As an Am- 
plifier 279 

CHAPTER XXVIII. 

Vacuum Tube as a' Generator of Undamped Oscillations — Sum- 
mary of Radiotelephony — Receiving 297 

Radio Dictionary 315 




Copyright, Underwood & Underwood, N. Y. 
NINE-INCH ANTENNA PICKS UP EUROPEAN RADIO MESSAGES 
Photograph shows a coil antenna nine inches square, yet powerful 
enough to receive wave lengths of many thousand meters. This coil 
when connected to an extremely delicate receiving apparatus will detect 
rarJio signals from European stations. This was made at the Bureau 
of Standards. Washington, D. C. 




Copyright, International 

FLORIDA FARMER GETS DINNER CALL BY RADIO 
Here's Daniel Talbot, a farmer of Florida, whose immense acreage 
takes him for some distance from his farmhouse and out of the range 
of sound of the dinner call. So he's rigged up a small radio set which 
he attached to his plow. When it's time to eat, Mrs. Talbot, at their 
home, sounds the call through the transmitter, which Farmer Talbot 
picks up while at work. 



CHAPTER I. 

Eomance and Marvel of the Wireless — Radio the Sensa- 
tion of the Age — Most Spectacular Electrical Develop- 
ment in all History — A New World of Science. 

OVER our heads there streams day and night through- 
' out the country an invisible traffic more dense than 
the surging motor cars and vehicles in our busy 
city streets. There are voices and music "in the air" 
and a new and marvelous world has been discovered for 
mankind to explore, through the development of radio- 
communication — the wireless telegraph and telephone. 

To what end the explorations may lead no one knows 
and few care to venture an opinion. What seemed to be 
true yesterday may not be true tomorrow. The radio has 
changed it all. Theories that were held to be good a short 
while back are found to be fallacious, and rules that were 
once laid down for the strict guidance of the technician 
in the field of electricity must now be disregarded. 

That a man in New York could project his voice into 
space so that his song or his message could be heard 
in Chicago or San Francisco — in London or Paris — 
without resorting to the use of a wire to convey the 
sounds of his voice would have been regarded as prepos- 
terous a few short years ago, and the man who had the 
temerity to claim that he could do such a thing would 
have been regarded as a fit subject for observation in a 
sanitarium. 

And yet, men are talking not merely from one city to 
another through space, but they are talking to thousands 
all over the face of the universe at one time and with one 
effort and one voice because of radiotelephony. 
2 17 



IS RADIOTELEPHONY 

It would require the imagination of a Scheherazade, 
who entertained her king with marvelous tales on a thou- 
sand and one Arabian nights, to conjure up the wonder- 
ful things that may be accomplished through the medium 
of radio communication, and to describe the effects upon 
the world of the discoveries that have been made in the 
field of electricity within a few short years. 

For several years prior to and during the great war 
there had been the ripping crash of the wireless telegraph 
in the airlanes overhead, but it was only after the war 
that the radiophone came into its own, opening up a 
revolutionary field of human achievement. Almost in a 
day radiotelephony became the rage in America. The 
wireless telegraph with its great sparks possessed many 
seemingly mysterious and spectacular qualities viewed 
from the popular standpoint, but it made no such appeal 
to the imagination as did the radiophone when some 
realization of its possible uses became known. 

EVERY HOME AN AUDITORIUM. 

The fortunate owner of a radio set was privileged to 
enter the new world of the air. Men of science made sev- 
eral important discoveries and perfected devices which 
made it possible for the veriest novice to pick out of the 
air words, messages or music sent broadcast over the 
face of the earth from powerful electric stations. 

The radio owner was enabled not only to enjoy news 
and entertainment furnished daily by broadcasting sta- 
tions in his own city or near-by centres, but he had entree 
to the radio amusements of cities hundreds of miles away 
and the cozy radio room in any radio-equipped residence 
might easily become the auditorium for an orchestra 
playing in a city 300 or 500 miles away. 

The fact that such things were possible with any sort of 



MIRACLE OF THE AGE 19 

a device would have been sufficient to arouse world-wide 
interest, but the fact that any intelligent boy can for a 
few dollars devise a radiophone with which he can hear 
the mysterious messages and waves of music that he 
knows are floating somewhere overhead, adds to the in- 
tensity of the interest and causes the radiophone to gain 
a portion of popularity within a few short months that 
has probably never been attained by any other device in 
the history of the world. 

It is not the purpose at this point to describe the wire- 
less telegraph or telephone, but it is important to note 
that the amateur radio enthusiast may for as little as $3 
or $4 construct a receiving outfit with which he can 
"listen in" on messages and hear music broadcast from 
stations within ten or twenty miles of him. 

But once he is able to hear the station within a short 
distance of him his ambition grows ; he wants to hear one 
at a greater distance, and his demand for more efficient 
equipment becomes insistent. When he gets a better re- 
ceiving set and hears Pittsburgh, or Chicago, he wants 
to hear San Francisco, the next day Honolulu and then 
he wants to get Mars. 

RADIO DEMANDS ENORMOUS. 

All this is natural because human desire is a progres- 
sive ailment, and out of it there develops the spirit of 
competition and rivalry. The boy with the $10 receiving 
set who heard a station further away than did his neigh- 
boring boy friend with a more expensive set, had achieved 
something, and he had something to be proud of and of 
which he could boast to his friends. 

A gauge of the intense interest aroused in the new 
science-sport is provided by the records of factories en- 
gaged in turning out parts for the construction of radio 



20 KADIOTELEPHONY 

sets. During the latter part of 1921 and the first half 
of 1922 it was impossible for the makers to keep up with 
the demand. This was especially true of those manufac- 
turing vacuum tubes used as detectors, amplifiers and 
also as transmitters. 

In England crystal detectors were chiefly used in the 
early stages of radiotelephony, and this was true in 
America for a time, but with the increasing knowledge 
and experience of the amateur there came a sweeping de- 
mand for better results which the vacuum tubes give and 
the makers were swamped with orders. In the first 
eleven months of 1921 factories working for one of the 
largest radio corporations made an average of 5,000 a 
month. Then broadcasting became popular and the calls 
for tubes jumped to unforeseen proportions. 

DEMANDS HELP BUSINESS. 

By the end of December, 1921, the factories had in- 
creased their output to 40,000 tubes a month. Then the 
schedule was jumped to 60,000. With the establishment 
of every large broadcasting station came increasing de- 
mand and the output jumped to 100,000, then 150,000 a 
month and finally to 175,000 — all within a period of about 
half a year. That the makers were confronted with diffi- 
culties in meeting this increase in business goes without 
saying, when it is understood that the tubes are made 
principally by hand. 

The sweep of radio enthusiasm over the country natu- 
rally had a very salutary effect from an economic and 
commercial standpoint. The world of industry was suf- 
fering from stagnation and business was "slow" when 
the wave swept over cities and towns causing unusual ac- 
tivity in all concerns dealing in or having to do with elec- 
trical equipment and supplies and thousands found oc- 
cupation who had been in idleness. 



MIRACLE OF THE AGE 21 

Great department stores and musical houses found in 
the radio a loadstone that drew thousands into their 
places and commercial reports seem to indicate that the 
general improvement in business conditions in the first 
half of 1922 was in part caused by the interest in the 
radio. 

RADIO BOON TO FARMER. 

There is political significance too, in the advent of the 
radio, for everyone knows the power of personal appeal 
to the voter and the sometimes difficulty experienced by 
political candidates and spellbinders in reaching the right 
individuals. The radio opens a new field of possibility 
in this direction for the candidate who has a message to 
deliver to his constituents can send his own voice into their 
homes. He can to all intents and purposes make a call 
and talk directly to people who have never been avail- 
able to him, putting actual personality into his message. 
Moreover he can talk to thousands of voters at one time, 
and since it is necessary to reach the woman in the home, 
because of their recent enfranchisement, the radio will 
solve one of the problems which has been puzzling the 
political aspirants and bosses everywhere. A number of 
candidates in various parts of the country have made 
good use of the radio and with the increasing number of 
receiving sets in operation its use will become effective. 
In keeping with this thought Senator New, of Ohio, when 
faced with the impossibility of keeping an engagement in 
which he was to deliver an address to women in his own 
state, kept his promise by arranging to have an adequate 
receiving set installed for the women and broadcast his 
address from Washington. 

"Where the ordinary means of communication are lack- 
ing is where the radiophone reigns supreme and it is 
proving a boon to the farmer, not merely as a source of 



22 BADIOTELEPHONY 

information from the wide world, or of amusement but as 
a convenience. On one great farm in the west, the owner 
rigged up a small receiving set and installed a small 
transmitting station so that his wife could send messages 
to him wherever he might be on the big acres that com- 
prise his farm. The Chicago Board of Trade also in- 
stalled a station from which to send out reports, market 
quotations and similar matter to farmers of the west. 

In some of the major hotels of the country efforts have 
been made to connect up various rooms in the hotel to a 
single receiving station so that any guest who desires to 
hear might do so without leaving his room. In other 
places a radio room has been equipped so that the guests 
can assemble and hear the concerts and talks sent through 
the ether. 

AN AUDIENCE OF 100,000 PERSONS. 

We are accustomed to regarding an audience of 3,000 
or 4,000 persons as representing a very large gathering, 
but if one can picture a mass of probably 100,000 persons 
listening to one opera, it will give some conception of 
what the radio accomplishes where no other device could 
serve. 

One of the first picturesque steps of the Westinghouse 
Company in Chicago was to broadcast the opera of 
"Samson and Delilah" from its set on the Commonwealth 
Edison Station in the western metropolis over an area 
approximating 700,000 square miles through the middle 
west. The opera was heard by people scattered from New 
York to Kansas and from Minnesota to Kentucky. 

Unlike many other broadcastings this one was made 
under actual operatic conditions. It was begun with an 
address by Mary Garden, the Director of the Chicago 
Opera Company and was followed by the rendition of 
major parts of the opera. The transmission of the opera 



MIKACLE OF THE AGE 23 

was secured by placing small transmitters high up in the 
wings of the auditorium stage of the Chicago Opera 
House, from whence the tones were earned to the West- 
inghouse station. 

Notices regarding the test had been previously sent 
abroad and broadcast to wireless stations throughout the 
west, and on the night of the first wireless opera thou- 
sands listened-in. The Westinghouse Company and the 
Opera Company received letters from Texas, North Car- 
olina, Vermont, Minnesota, and even Canada. 

The significance of this is greater when it is realized 
that until the advent of the radiophone the opera, except 
on rare occasions, was a closed book to thousands of farm- 
ers and ruralites scattered over the broad lands of the 
middle west. 

The demonstration is proof that science has bridged 
another epoch and humanity is richer. Edward Bel- 
lamy's dream, presented in his memorable " Looking 
Backward,' ' published in 1888, is realized. He visualized 
a great cooperative commonwealth of the twenty-first 
century in which nobody need leave tbeir homes to hear 
the great musical concerts. Mr. Bellamy painted a pic- 
ture of family groups gathered in the home, where they 
pressed a button and concerts commenced which lasted 
for a considerable period each afternoon and evening. 



CHAPTER II. 

Simple Facts about Radio — Equipment — Transmitting 
and Receiving — Functions of Various Parts — Common- 
place Definitions — Antenna, Receiver, Detectors. 

BEFORE one can comprehend the vast possibilities 
of the radio and the intricacies of the new science in 
electricity it is necessary to have a general under- 
standing of what it all involves and some idea of how 
and with what means and devices scientists have obtained 
the wonderful results. 

Radio communication involves three definite opera- 
tions: First, there must be a suitable source of radio 
energy, which is designated the " transmitter " capable 
of imparting the energy to space, or the ether, as the 
scientists call it. Next, the radio energy converted into 
vibrations of the ether, is projected through space in 
wave circles over the surface of the earth. The waves, 
naturally gradually lose their power as they extend far- 
ther and farther away from the source, just as the waves 
produced in a body of water by the throwing of a stone, 
decrease in height as the circles increase in size and the 
distance from the centre becomes greater. The third step 
is to intercept the ether waves at any desired point — to 
catch whatever message has been projected. For this 
purpose a receiving set is used. 

It is obvious that the more powerful the transmitter 
the further the circle of ether waves will extend, and that 
the more sensitive the receiving set, the further away 
from the original point of transmission the waves will be 
felt. For this reason waves that may be felt by one re- 

24 



MIRACLE OF THE AGE 25 

ceiving set at a distance, of say, two hundred miles will 
not be detected by another set less sensitive. 

Effective radio service, therefore, resolves itself into 
the matter of distance from the transmitting station, and 
the receiving set employed. To the individual interested 
in the newest science the receiving set is the one big thing. 
To this there are five essential parts. The antenna, the 
lightning switch, ground connection, the actual receiving 
set or device, and the phone. 

The received signals or waves come into the actual re- 
ceiving set through the antenna and ground connection. 
The antenna is therefore a highly essential factor in the 
big system. This is simply a wire or set of wires sus- 
pended between two highly elevated points. 

If you are at all familiar with ants you will have some 
idea of what the antenna is. The electric experts have 
taken the word antenna from entomology. The wires are 
"sensitive feelers" which detect the waves that strike 
them in the air or ether space. The waves are projected 
from the transmission station and when they reach the 
antenna extending up into space they impart to it the 
identical wave motion. 

If you lay a block of wood on the surface of a small pool 
near the bank or shore, and strike it sharply, it will bob 
up and down on the waves. A similar block of wood laid 
quietly on the water at the opposite side of the pool will 
have imparted to it the same motion when the waves 
created by the striking of the first block have extended 
across the pool. Both blocks will follow the wave undula- 
tions and move together. This is precisely what happens 
in radiotelephony. The antenna when struck by the 
ether waves moves precisely as do the waves projected 
from the transmission station. 



26 BADIOTELEPHONY 

The antenna and the ground wire with the lightning 
switch constitute a protective device when used together. 
When the switch is closed the antenna and the ground 
form a lightning rod to protect the building to which they 
are attached as well as the sensitive receiving set. 

AN ADJUSTABLE SENSITIZER. 

The principal parts of the actual receiver are the 
" tuner and detector." Stripped of its technical descrip- 
tion the tuner is a knob or lever which modifies or am- 
plifies the sensitive qualities of the machine so that it is 
susceptible to the wave motions which it is desired to 
receive. It might be termed an adjustable sensitizer. 

If one wore a pair of spectacles which permitted only 
a given shade of pink light to pass through them it might 
be said that the wearer was tuned for that shade of pink 
light. Other shares of light would not be seen by the 
wearer. 

In radio this same situation is found. Eadio waves are 
of different values or wave lengths, which are referred to 
as lengths in meters. One station uses a wave 360 meters 
long; that is the transmitter is keyed up to send out ether 
waves of this length. When the knobs on the tuner are 
manipulated to catch this wave they must be turned to 
a point where in effect the machine vibrates to these 
wave lengths. 

Nearly everyone has heard a violin, guitar, mandolin or 
other stringed instrument standing or lying in the room, 
suddenly vibrate in sympathy with a note struck on a 
piano. The same effect is produced when the radio re- 
ceiving set gets in tune with the transmitting station. 

So it is that if the receiver is tuned down to waves of a 
hundred or two hundred meters, the message or music 
carried on the waves, is heard from some point closer at 
hand. If the machine is tuned higher the vibrations from 



MIRACLE OF THE AGE 27 

a high powered station that sends across the Atlantic may 
be felt. 

This timing of the transmitter and of the receiver is 
what will make it possible to have what is known as selee- 

tivitv in radio commnnication. The machine that is tnned 

*> 

to three hundred and sixty meter waves will not record 
those sent ont in waves of two hundred meters. And so 
finely adjusted are the more pretentious radio sets that it 
is possible to shut off waves of a very small percentage of 
difference in variation. A wave of 200 meters length may 
be received and one of 205 meters length shut out. 

By standardizing the use of wave lengths it is proposed 
to prevent confusion in the great ether channels of traffic 
above. It is planned that music shall be sent out in waves j 
of one length, business reports in waves of another 
length, lectures in a third length, weather reports in still 
another, and so on. 

WAVE LENGTHS FOR NATIONS. 

The Government will reserve for itself the right to use 
waves of a specified length for all official communications 
and statements, and in international affairs if we wish to 
hear London or Liverpool we shall tune to one wave 
length, and if we wish to hear Paris we shall tune to an- 
other. The range of wave lengths is almost unlimited, in 
so far as variations are concerned and for this reason it 
would be possible for every Nation to have its own wave 
length. 

This plan will of course prevent one message from in- 
terfering with another, and the program in this direction 
is being worked out. Something about this is discussed 
elsewhere. But to return to the physical aspects and 
qualities of the actual receiving apparatus. 

Technically the process of tuning is accomplished by 
varying the induction and capacity. Inductance may be 



28 EADIOTELEPHONY 

defined as the transferring of a current from an elec- 
trified to an unelectrified conducting body without actual 
contact. The possibility to do this is one of the phenom- 
ena of electricity which has made the radio possible. 

WHAT CAPACITY MEANS. 

Capacity is a term used largely in connection with con- 
densers and refers to the ability of the condenser to store 
up energy. In common usage the inductance variation is 
obtained by what are termed steps — by taking taps at 
every so many turns of wire wound on a large tube, the 
taps being connected to the points of a switch or binding 
posts, or again by what is known by a sliding contact. 
That is a coil of wire through which the current must flow, 
and which is arranged so that a point or finger can slide 
along the surface of the coil and establish an electrical 
contact at any preferred point. This is called a tuning 
coil. In the finer apparatus there is used what is termed 
a variometer. In this movable coils are arranged to 
rotate within a fixed coil, so that the electric current may 
be made to flow in the same direction in both coils or in 
opposite directions. When the windings are in the same 
direction the inducements are greatest ; when arranged in 
opposite directions, they are in what is known as " buck- 
ing' ' position and the inducement is lowest. 

The condenser is a device which determines the ca- 
pacity as already indicated. The commonest type con- 
sists of a group of fixed aluminum or brass plates and a 
set of movable plates which pass in and out between the 
stationary plates when a handle or lever is turned. The 
plates do not touch each other and the surrounding air 
serves as what is technically known as a dielectric or non- 
conductor. 

Besides tuning to the proper wave length it is neces- 
sary for the receiver to have a detector and a telephone 



MIRACLE OF THE AGE 29 

receiver. The detector may be of what is termed the 
crystal type, or the vacuum tube type. The former is the 
simplest and least expensive, though probably not as ef- 
ficient. Still there are many fine machines constructed 
with this type of detector. 

CRYSTAL DETECTORS. 

It has been discovered that many crystals possess the 
qualities essential to make a detector — i. e. the prop- 
erty of suppressing one of the impulses of an alternating 
current of electricity. It is absolutely necessary that this 
be accomplished to make radiotelephony possible for the 
vibrations set up in a receiving set are so rapid — have 
such a high frequency — that they cannot be heard in the 
ordinary telephone receiver. 

The crystal makes it possible to separate one alterna- 
tion from another and thus produce spurts of electricity 
in one direction only. The crystal might be called a 
deterrent. Certain forms of carbide of silicon, (carbor- 
undum), molybenite and hessite are among the best 
known crystals of this sort. There are also crystals 
which when used in pairs — in contact — are better con- 
ductors in one direction than others, and serve the same 
purpose as the vacuum tube, described elsewhere. Among 
these are galena, graphite and zincite. 

The purpose of the detector is obviously to transform 
the signals or waves, which have been tuned in, into audi- 
ble sounds in the telephone receiver. They slow them 
down. In use the crystal detector is kept in contact with 
a metal point, or another pointed crystal. A sensitive 
spot is found on the larger crystal, but the detector must 
be adjusted as the larger crystal from time to time loses 
its sensitiveness. For this reason the vacuum tube is 
more efficient, for it is constant in its service, more easily 
adjusted and many times more sensitive. 



30 RADIOTBLEPHONY 

The part played by tlie antenna — frequently called the 
aerial — has already been stated, but its physical relation 
to the outfit should be thoroughly understood. It may be 
anything from a single wire to a group or great series of 
parallel wires reaching out and up into space. 

For the radio equipped to receive the ordinary broad- 
casting, a wire about 100 feet long stretched between the 
house and a tree or a high pole may serve, but two wires 
will generally prove more effective, and if more than 100 
feet long the chances are that there will be a higher de- 
gree of efficiency. The wires must be insulated. 

Such an aerial would not of course, serve for a great 
broadcasting station. The radio Central at Rocky Point, 
L. I., by way of comparison, uses an aerial one and one- 
half mile long and 410 feet high and is composed of 16 
wires. For amateur receiving the size and kind of an 
aerial depends upon several things. With a better grade 
of receiving apparatus results may be obtained with a 
short aerial that could not be obtained with a poor re- 
ceiving set, and conversely the longer antenna should be 
used with the less efficient receiver. 

As in almost everything else that has to do with radio, 
the changes that take place are very rapid and one of the 
later forms of antenna developed is called the "loop." 
Instead of employing an aerial with the ordinary connec- 
tion, a simple frame of wood, sometimes square, like a 
window frame, but more often in the form of a letter X, 
with half a dozen turns of wire around it, is employed. 
Such a loop may actually be used by suspending from 
the ceiling in the house, but since it cannot intercept as 
much energy, the deficiency in the amount of energy ab- 
sorbed must be made up by the higher efficiency of the re- 
ceiving apparatus — one with more powerful amplifica- 
tion. 



MffiABCLE OF THE AGE 31 

The loop is considered one of the wonders of radio 
development because it not merely intercepts the waves, 
but can be used as a direction finder. It will indicate the 
direction or source of the waves. The wire is wound 
around the outside of the frame. 

LOOP LOCATED GERMAN SHIPS. 

During the World War the British fleet located the Ger- 
man fleet by tracing the source of the wireless messages 
sent out from the German flagship by using the loop as a 
direction finder. The loop acts best when turned in the 
direction of the oncoming waves — that is when the edge 
of the frame is turned toward the source of the wave 
centre. It is less efficient when the frame is sidewise or 
at right angles to the waves. 

This being so, it is plain that by turning the frame the 
source of the waves can clearly be determined. Some in- 
teresting things have been accomplished by the use of the 
loop as a finder as will be shown in another chapter. 

In the technical discussion of the wireless two terms 
that may perplex the uninitiated are " audio-amplifica- 
tion ' ' and ' * radio-amplification. ' ' A clear understanding 
of what is meant by these expressions may be gained 
from the statement that audio-amplification is the ampli- 
fication of the sound waves after detection — the use of 
devices which make the wave sounds more audible after 
they are picked up. Eadio-amplification, in a general 
sense, is amplification of the waves before detection — the 
use of amplifiers which makes the feeble waves more 
easily detected in the receiver. The understanding of 
these facts is highly essential in the operation and con- 
struction of receiving sets and should be carefully studied 
by anyone desiring to go into the theoretical or practical 
sides of the subject. 



CHAPTEE III. 

The Wirleless Machine — The Telegraph and Telephone 

— A Million Users in a Year — The Medium of Universal 

Communication — Useful and Amusement Providing. 

MEASUEED in units of time the world is now about 
one-tenth of a second wide. Eadio is the new in- 
strument with which we measure the world's 
width in this astonishing fashion. Viewed through this 
magic reducing glass created by man the earth, for all its 
eight thousand miles diameter, seems to have shriveled 
into a ball so small that it might be held in the hand of a 
playful child. 

San Francisco no longer is three thousand miles distant 
from New York. It is within speaking distance. The 
whole world has become one vast auditorium in which the 
speech of one man may be heard by all. Chinese and 
Patagonians, Esquimaux and Africans, and Japanese and 
Americans have become next-door neighbors and may 
hear together the spech of the Parisian, the Londoner, 
the New Yorker or the Mexican at one time. And all of 
this because of the wireless — the Age Miracle. 

With the strides that wireless has made it is no idle 
dream to picture a woman comfortably ensconced in her 
boudoir sipping her morning coffee and listening to a 
tempting list of offerings at her favorite shop. The wire- 
less has formed the connecting link between grand opera 
as rendered in Chicago or New York or Philadelphia and 
the fanner's daughter sitting at her father's fireside. 
Train orders now are sent miles through the chartless 
ether to the swiftly-flying train. And the end is not yet. 

32 




C 6C 


J=C 




rt* 


t, W 


0) 01 


CO 


a> 


0.23 


* 




X-3 


ftd 



O ^^ 

W ° V 

ft u£ 

J 3 02 

I— I TO f-i 



w +-> 



CQ 

£ o 5-° 









-O 

P 



II 



>>° 



fc> * TO 




o qj 



o 



£ ft- 23 






P *-2 
H 






A S 

• ~ °>> 

^ 72 « « 
„■ H Si > 

9 W 



a; a; 



be 

P . 






o ^ 



*h a; 

O 03 




£<££ 

3 o i 

• ^ 

r o o 
42 

*K 

<u 43 

r;<DO 

to'o 

l !i 

« «* S 

IP g m 



►J ° 

§ 

s 

O 

P 



w 2? £ 
£ o 

£■* 

« ^s 

M M ° 
cj «, to 



05 

o 



l«g 

43 fj ^cu 

m . m 

tn tn oJ 

a b*i 

_, S- 0) 

rt rt > 

■ £ rt 

^3^2 03 





P.42' 



MIRACLE OF THE AGE 33 

Man is but beginning to realize the possibilities of this 
most wonderful of inventions. 

Manufacturers of electrical supplies — and more espe- 
cially those who are foremost in the development of radio 
equipment and parts — have had from the beginning but 
one stoiy to tell, and that was that they were more than 
swamped with orders. Distributors of apparatus, asked 
about radio, have assumed a bored air, and remark quite 
nonchalantly, ; * Oh, yes, we could sell hundreds of outfits 
but — try and get them. They are sold the minute they 
hit our store. ' ' One large company had more than fifteen 
million dollars worth of orders on hand and was refusing 
to accept more until production had to a definite extent 
caught up with the ever-increasing demand. The Elec- 
trical World is sponsor for the statement that within a 
year instruments in use increased from fifty thousand 
sets to more than a million in constant use. In many 
cases business men have added their wireless call and 
their wave length to their letterheads. 

GLOBE DOTTED WITH STATIONS. 

But even as this industry — this wonderful invention- 
gets momentum and begins to spread its usefulness to all 
corners of the earth immediately there arises a difficulty 
and a very serious one. Who shall decide what is to be 
done about distributing? Which nation is to be given 
prior rights to a certain wave length; For, it is easy to 
see that immediately there have been all sorts of compli- 
cations occasioned by the sending out of wireless im- 
pulses in all directions into the trackless air. There must 
be traffic rules, even as there now are traffic rules for the 
use of the air by airplanes. 

Every region of the globe is becoming dotted with send- 
ing equipments installed at an expense of several hun- 
dreds of millions of dollars. Even experts are finding 



34 RADIOTELEPHONY 

themselves from day to day very much at sea concerning 
wireless, so fast its progress has been, so wide its scope 
has become and so limitless is its field. What may be done 
in the future is merely a matter of conjecture. Already 
automobiles have been equipped with receiving apparatus 
and already there has been found a way for individuals to 
carry along with them apparatus which will permit them 
to pluck from the air a "message from home." 

All of this leads to a consideration of several compli- 
cating angles of the problem. What effect will the per- 
fecting of the radio equipments have upon the present 
method of transmission of power, and of transmission of 
messages themselves: Surely, the recent work that has 
been done by Dr. Steinmetz the electric wizard with arti- 
ficial lightning would tend to indicate that there is possi- 
bility of the wireless transmission of power. Think of 
the tremendous possibilities of that one item alone J Is 
there any limit to what will grow out of this invention? 
And, then, what after all is wireless ? 

ELECTRO-MAGNETIC WAVES. 

Wireless actually is nothing more nor less than the 
sending and receiving of electro-magnetic waves through 
the ether. Think of the earth as being a great big ball 
surrounded by space. Eemember that when we say 
space, we refer to the scientific meaning of that term and 
include all interstices between the molecules or atoms 
that go to make up a mass. Thus, there is space in a 
brick, in a tree, in a piece of coal, for in each case the mat- 
ter is made up of constituent parts which are formed to- 
gether according to the wonderful laws of cohesion and 
adhesion — but which have between them a certain amount 
of space. 

We have mentioned electro-magnetic waves. What are 
they? They actually are disturbances, vibrations if you 



*\ 



MIRACLE OF THE AGE 35 

Trill, traveling through the ether surrounding this great 
big earth of ours. The sunlight that lights our daily ac- 
tivity — and, indirectly by moonlight, our nightly move- 
ments — is nothing more nor less than the result of electro- 
magnetic waves. However, the waves of the sunlight are 
of such length that they are discernible to the human eye. 
Then, too, we know that the sun generates heat and that 
Man generates heat by other and artificial means. This 
heat is discernible by us through what is known as heat 
waves. These heat waves are simply electro-magnetic 
disturbances of such length as to be discernible by the 
human body through the sense of feel. 

WAVE LENGTHS UNLIMITED. 

Both light and heat are the same thing as the phenom- 
enon with which we are dealing when we think of the 
wireless or radio. They are simply electro-magnetic 
waves or disturbances. The wave length of light is about 
one-fifty-thousandth part of an inch. The wave length of 
heat is five times as long — one-ten-thousandth part of 
an inch. The wave length of wireless varies from 100 
feet to two miles or more. Thus, you see that these waves 
are beyond the recognition of the human system and have 
to be converted or ' ' tempered down ' ' to the human mech- 
anism before they make their true impression. This 
is done through the radio receiving sets that have been 
perfected. Wireless, therefore, is simply the creation of 
artificial wave lengths of such vastly greater lengths than 
heat waves and light waves as to be readily distinguish- 
able, and the ejecting of these waves out into the ether 
so that they may be intercepted or picked up by other 
men. 

The variety of lengths that may be sent or "broad- 
casted' ' is without number. Thus, waves 500 feet long 
or 2,000 miles long may be sent out and man can inter- 



36 KADIOTELEPHONY 

cept and interpret them, and any two persons or any 
group desiring to communicate can "tune" or adjust 
their sets to receive only the waves of the length in which 
they are interested and thus eliminate or weed out all 
other waves or impulses. Thus it is possible for an ama- 
teur to broadcast on a comparatively short wave length 
at the same time that a larger public sending station in 
the same city is sending out its daily program. Due to 
the difference of the wave lengths, there is no conflict. 
This is what is referred to as selective receiving. 

DIFFICULTIES WITH WAVE LENGTHS. 

It is not now possible to refine closer than one per cent, 
so it may be seen readily that waves of 5,000 feet would 
interfere with waves of 4,950 or 5,050 feet. In other 
words we cannot detect the difference between waves of 
these lengths. Since it is these long waves that are used to 
transmit messages over longer distances (inter-continent- 
al messages, etc.) it will be of great interest to the whole 
world to know how and what international regulations 
will be possible to control the sending of these waves 
which, it would seem, would be bound to give rise to in- 
ternational complexes. It readily is seen how funda- 
mentally important the radio is to become to corpora- 
tions owning and operating ships, in keeping in touch 
with their vessels during the course of their voyages. 
The refinement of the process of selective receiving and 
perhaps some equitable arrangement of the wave lengths 
of the various nations may serve as a solution to the 
present big problem — not to say tangle. Perhaps one 
single invention may increase the possibilities and use- 
fulness of the radio tenfold. 

Wireless radio communication may be said to be at the 
present time of two distinct types. There is the original 
form of the wireless, which is based upon practically the 



MIRACLE OF THE AGE 37 

same principle as brought forth by Marconi. This is 
what is known as the trne wireless, or so-called "univer- 
sal" wireless. Then there is the type known as "wired 
wireless." This latter type perhaps of the two presents 
the greater possibilities for future development. It is 
based on the scientific work that has been done by Major- 
General George 0. Squier, of the United States Army. 

"Universal" wireless is sent out broadcast by means 
of a mechanical device which launches into the ether 
electro-magnetic waves of uniform and exact, as well as 
predetermined, length. The length of the impulse and 
the amount of time that elapses between them determines 
the message. In other words, the code is based upon 
these two features. The dots and dashes of the Morse 
telegraphic code, so familiar because of the years of gen- 
eral use, are obtained by variance of the duration of the 
wireless impulses. 

The distinctive feature of this method of sending (and 
perhaps its cardinal drawback) is that impulses sent out 
in this manner are impulsed or scattered in all directions. 
The message is imparted in every direction impartially. 
In other words, radiation takes place, just as every cor- 
ner of a room would be warmed by rays from a round 
stove placed in the center of the room. This makes it 
possible for any message to be picked up at any point, 
providing the receiving set is properly "tuned." The 
wide difference between the amount of energy required 
for this type of broadcasting and for receiving of mes- 
sages broadcasted in this way is readily conceivable. At 
the present time it requires well over a trillion times as 
much energy to send forth a message that will "carry" 
across the Atlantic or the Pacific as it will require to pick 
up that message on the other side. 

And so it readilv can be seen that this universal method 



38 RADIOTELEPHONY 

of transmission is very costly, relatively speaking. Nec- 
essarily, the simple rules of mechanical economics show 
this fact. The impulses traveling as they do in all direc- 
tions around the circle of 360 degrees, must of necessity 
develop a tremendous amount of waste energy, sending 
forth the impulses that travel in every direction other 
than the one particularly desired. Then, too, it readily 
may be seen that any message sent forth in such a fashion 
immediately becomes the property of anyone who can 
"tune in" with that message and hence there is absolute- 
ly no secrecy possible in connection with this method. 

RADIO FOR TRANS-OCEANIC WORK. 

When radiotelephony first became known to the public 
in general a great deal of speculation was indulged in as 
to what the efleet of this invention and of the improve- 
ments incident to it would be upon commercial enter- 
prises such as Transatlantic cables, long-distance teleph- 
ony, etc. Especially in connection with Trans-oceanic 
communication it would seem that the likelihood of the 
wireless method of communication becoming a serious 
competitor of the present cable system is very small in- 
deed. The high cost of installation of plants sufficiently 
large to take care of transmission of the waves and the 
high overhead expense incident to the maintenance of 
these plants preclude such a possibility. The laying of an 
oceanic cable seems to be practically the first and the last 
cost. Comparatively speaking the cost of the energy 
necessary to drive a message across the ocean through a 
laid cable is a bagatelle as compared with the present cost 
of wireless impulse. Then too, the item of privacy will 
have a large consideration for a period of time, or at 
least until further refinements are possible. The theory 
of wired wireless, as advanced by General Squier, seems 
to have proved itself out as being very sound and its 



MIRACLE OF THE AGE 39 

practical application has been accomplished. General 
Squier has proven the fallacy of the belief that wireless 
and wired telegraphy and telephony are separate and dis- 
tinct propositions. 

GENERAL SQUIER'S DISCOVERY. 

General Squier came into the wireless field at an ex- 
tremely fortunate time, when certain other improvements 
that were being constantly effected, dovetailed in beau- 
tifully with the experiments that he made. He went 
ahead without bias on the theory that there might possi- 
bly be a real connection between wired and wireless com- 
munication. And his reasoning along this line was 
prompted by a very simple fact. In sending out wire- 
less impulses, the waves are conducted along wire an- 
tennae, from which they are led off into the air and pro- 
jected into space. In other words, they are guided those 
initial few feet by the wired antenna, much as the rifle 
bullet is given its initial direction and mode of flight by 
the rifling or spiral grooving of the barrel. Wireless 
waves, although there are projected in the "universal" 
method in broadcast fashion, nevertheless follow the 
curve of the earth. This they must do because of the 
trend of the ether surrounding the earth. What held 
those waves parallel to the earth's surface instead of 
permitting them to fly off into thin ether at a tangent to 
the earth's surface? Surely, reasoned General Squier, 
it must be the attraction of the earth or some other effect 
similar to that of gravity. Could not a substitute for this 
attraction be effected? His first comprehensive experi- 
ments were conducted in 1910, showing the time and 
thought that has been put into the development of his 
theories — theories which are just now actually finding a 
really big place in practical radio work — or commercial 
radio? 



40 EADIOTELEPHONY 

Briefly as possible, General Squier proved to Ms own 
satisfaction, and later on to the satisfaction of other 
scientists and experimenters along the lines of radio 
communication, that wave impulses set up along a wire or 
parallel to a wire would follow the wire along its full 
length, as far as the energy behind the impulse would 
permit. The wire acts as a sort of chaperon to the waves 
and conducts them along through the air in the way they 
should go. At the time General Squier began his experi- 
ments long-distance telephone messages were conducted 
over strung wires and were sent One Message at a Time. 
However, General Squier 's discovery made it possible to 
transform this one carrying wire into a sort of guide wire 
making possible the transmitting of more than one mes- 
sage — in some cases as high as forty or fifty — through the 
use of the one wire. This does not mean in any sense of 
the word that more than one message can be sent Through 
a wire at one time but it does mean that the wire can be 
used to guide messages so that more than one message 
can be sent at one time, the wire guiding those messages 
and seeing to it that they stay in the narrow path which 
they were intended to travel. It now is possible to carry 
between New York and Chicago over one wire five dis- 
tinct and separate telephone conversations and as high 
as eighty telegraph messages, General Squier 's theories 
or rather the developments that have grown out of them 
have been styled multiple telegraphy, meaning the tele- 
graphing at one time of more than one message or im- 
pulse. Thus the wireless in this case has greatly aided 
the well-established and essentially correct method of 
wired telegraphic communication, but that for the several 
reasons outlined it will not supplant the wired system. 

The possibilities of wireless communication may read- 
ily be seen. Messages which do not of necessity have to 



MIRACLE OF THE AGE 41 

be made strictly private can be "broadcasted" efficiently 
by means of the radio. Messages which are strictly pri- 
vate in their nature cannot as yet be handled with this 
feature of privacy intact. Later, refinements might over- 
come even that point. Nothing seems impossible in this 
age. Any person or group of persons with a message 
which lends itself properly to broadcasting will find in 
the radio, even as far as it has been developed, a wonder- 
ful medium of communication. Already organizations 
like department stores, lecture organizations, etc., are 
broadcasting programs of amusement or education as- 
pect. The scope of this type of communication for ex- 
tension of our present educational features is without 
limit. Think of being able to sit in your home at night 
and by simple adjustments to "tune out" until you have 
coming in to you in distinct and easily discernible speech 
a lecture on engineering, or bookkeeping, or salesman- 
ship or advertising or what not. 

The government is sending out the official time, an- 
nouncing weather reports, giving out crop statements 
and advice to farmers. The Public Health Service figures 
that it is reaching a total of approximately 700,000 receiv- 
ing sets through this medium of communication, with a 
series of comprehensive and educational lectures on gen- 
eral health. Many other fields of usefulness are being 
developed from day to day and to enumerate the possi- 
bilities is but to recite a list which would be all too patent 
to the average reader. Suffice it to say that nothing has 
been given Mankind to date that is so full of promise for 
future benefit and growth and improvement as is radio- 
telephony at the present moment. 



CHAPTER IV. 

Effects and Influence of Wireless Communication on 
Civilization — International Relations — Educational Pos- 
sibilities — Future Developments. 

THE history of radio is a striking example of how 
scientists laboring in the field of pure research to 
accumulated knowledge and imagination can spur 
reach conclusions and make discoveries of vital impor- 
tance to the world. 

As early as 1867, James Clark Maxwell, an English 
mathematical physicist, laid one of the foundation stones 
for modern wireless telegraphy when he adopted and 
proved the theory that light is an electro-magnetic effect 
— not mere mechanical motions of the ether, but consists 
of electrical undulations. Twenty years later Heinrich 
Hertz, a German professor in physics, proved that Max- 
well's theory was correct by actually producing electro- 
magnetic waves in such a manner that their propagation 
through space could be examined. His experiments 
showed that they possessed many of the properties of 
ordinary waves of light but that the waves were longer. 
The waves he produced are the waves of radiotelegraphy 
sometimes referred to as "Hertzian waves,' ' and are the 
waves that transmit signals or human speech in radio 
communication. 

But neither of these great men realized that these 
waves could be used to signal through space without 
wires, and Guglielmo Marconi in 1894 was the first person 
to actually utilize the Hertzian waves to signal a short 
distance. Within a few years he had succeeded in using 
the waves to signal several miles. 

42 



MIRACLE OF THE AGE 43 

Now many thousand commercial wireless stations dot 
the face of the earth. Warnings are flashed to ships far 
out at sea, daily time signals are sent out from Govern- 
ment stations, and weather reports are flashed across the 
land. In the midnight hours when the multitude is asleep 
press dispatches are whispered from wireless stations 
throughout the land and picked up by the ocean grey- 
hound far out at sea, so that the cabin passenger on the 
boat finds on the breakfast table when morning comes a 
newspaper that contains important news found in the 
great daily newspaper on shore. 

The Navy Department issues an order and a few min- 
utes later it is in the hands of the commanding officer 
of a fleet of war ships a thousand miles away. Wireless 
links cities, countries and continents and wireless teleg- 
raphy and radiotelephony are part of the order of es- 
tablished things. 

WILL BRING NATIONS TOGETHER. 

It is not conceived that the radiophone can ever take 
the place of the regular telephone, because, for one thing, 
it is impossible to restrict a private message to the hear- 
ing of the one person for whom it may be intended. Any 
person who has a receiving set of sufficient efficiency may 
pick up the message if he sets his machine to attune with 
the radio sending machine from which the message 
emanates, but it is destined to serve a world of purposes 
which the ordinary telephone cannot fulfill. 

The President of the United States may use it to ad- 
dress a message to the people. Speaking in an ordinary 
tone of voice he could talk to millions of people at one 
time. Had there been in use the radiotelephone during 
the great war the Secretary of the Treasury might easily 
have appealed to millions everywhere to lend their money 
to the Government for war purposes — to purchase bonds 



44 EADIOTELEPHONY 

— It would not have been necessary for him to travel 
about the country and make repeated addresses to tell of 
the needs of the Nation. 

And what might have been the relationship of America 
to the other countries during the great war had the radio- 
phone been perfected to a point where it were possible to 
converse directly across the vast ocean ! There are those 
who see in the development of radiotelephony a new era in 
international affairs and relations. They believe that 
there can be no isolation of any nation when the whole 
world is but a score of seconds wide in point of time as 
measured by the speed with which the spoken message 
will travel around the sphere. 

A WONDERFUL FIELD FOR THE RADIO. 

Viewed from the standpoint of mechanical possibilities 
economy engineers hold that there is a wonderful field 
for long-distance work with the radiophone. The ex- 
isting systems of long-distance wires are expensive to 
construct and to maintain. They are subject to the whims 
of the elements — torn by the storms — and also wrecked 
by accident and the depredations of thieves. 

The wireless telephone will transmit the speech as well 
if not better than the wire phone and it has the distinct 
advantage that the initial cost is much lower than that of 
wire lines, while depreciation is smaller. The number of 
employees required is less and there is no necessity for 
purchasing franchises or right of way to put up poles and 
wires. The wireless telephone also has a distinct advan- 
tage in the marine service because it requires no opera- 
tor. Any officer on a vessel could take a message — any- 
body can operate the radiophone — and it is much quicker 
than the wireless telegraph with its code that must be 
read and translated. Moreover, the wireless telephone 



MIRACLE OF THE AGE 45 

on shipboard will permit a passenger to talk direct to 
his home. r 

As an aid to education the use of the radio promises to 
open a field of vast possibilities. Tuft's College broad- 
casted some of its lectures early in 1922, and the day may 
not be far off when the young man desiring to take a 
course in college can hear all of the required lectures 
without being compelled to leave his own home. Why 
may not the student in music receive instruction from the 
great singer in a distant city? So vast are the possibili- 
ties that they are almost beyond comprehension. 

AN ADJUNCT TO THE HOME. 

In many homes the radiophone has become as much an 
integral part of the family equipment as its brother of the 
wire. It has been tried and accepted until the luxury 
stage is a thing of the past, and it has become an essential 
for those who would keep well informed on world affairs. 

Varying atmospheric conditions on different nights 
make it all the more fascinating, for the most humble and 
inexpensive radiophone set may suddenly find itself re- 
ceiving from a station hundreds of miles distant for 
which more powerful stations have tried in vain on less 
favorable occasions. 

In one of his talks broadcast from the big General 
Electric Company Station at Schenectady, N. Y., Mr. M. 
P. Rice, manager of the station declared that when all the 
people of the United States possess or have access to re- 
ceiving outfits it will be possible for a speaker to address 
the entire population of the country at one time. 

This possibility he said made the radiophone the 
greatest publicity agent of all times for its broad scope 
made it reach as many people as all other publicity agents 
combined, but radio, in the very nature of things, accord- 



46 BADIOTELEPHONY 

ing to Mr. Rice, can only exert a powerful influence on 
the press, the pulpit, the schools and the theatre and not 
supplant them. 

The newspapers, by way of illustration, early in March 
coined a very interesting story of how Dr. Charles P. 
Steinmetz, electrical expert of the General Electric Com- 
pany had manufactured lightning in his laboratory at 
Schenectady, N. Y. Few more picturesque incidents have 
come to the attention of the public and nearly everybody 
had heard about it, but the newspaper stories did not 
compare in point of interest, or influence with the talk of 
Dr. Steinmetz himself about lightning which was broad- 
cast from Schenectady a few nights later, on March 23, 
1922. 

STEINMETZ TALKS OF LIGHTNING. 

Lightning, with its beauty and its pranks, has always 
been a subject of deep interest to the human race, not 
merely because it is feared, but because of the deep mys- 
tery that surrounds its origin. Dr. Steinmetz 's talk, 
probably heard on the radiophone by many who will 
peruse these pages, explained much that has not been 
generally understood and was as follows : 

1 i Of all the phenomena of nature, lightning is the most 
terrifying and, therefore, the thunderbolt always has 
been the attribute of the highest God. Until Ben Frank- 
lin showed that lightning is nothing but an electric dis- 
charge, like those of our electric machines, only vastly 
more powerful. Little further advance was made in the 
understanding of the nature and origin of lightning until 
recent years, when finally our knowledge had advanced 
far enough to solve the problem of lightning and its 
origin. 

"In summer, when the air is warm, water rapidly evap- 
orates. Warm air can hold a large amount of moisture as 



MIBACLE OF THE AGE 47 

water vapor. Thus during the summer days, the warm 
air covering the surface of the earth becomes moisture- 
laden, saturated with water vapor. Warm air is lighter, 
and therefor this warm, moist surface air begins to rise, 
Often also it is forced upward by two air currents or 
winds meeting. In rising, the air gets cooler, because the 
higher up you go, the lower is the temperature. When 
cooling, the air cannot hold the moisture which it held 
when warm, and much or even most of the water vapor 
of the air condenses to minute water drops, so very small 
that they keep floating in the air as clouds, without fall- 
ing. But these minute water particles of the cloud con- 
glomerate, thousands of them gradually, by their mutual 
attraction, come together into one larger drop, and when 
the drop has become too large to float in the air it falls 
down as rain. 

HOW LIGHTNING IS LET LOOSE. 

"Now each of these minute drops which form by the 
condensation of the water vapor contains a minute 
amount of electricity, as there is always some electrifica- 
tion of the air. It is too little to be noticeable. But when 
a thousand of such minute drops conglomerate into one 
larger drop, the electricity of the thousand small drops 
is collected in the one large drop. But the large drop does 
not have 1,000 times the capacity for holding electricity, 
but only ten times, and as it has to hold the electricity of 
the thousand drops from which it was formed, the elec- 
tricity is crowded together on it a hundredfold, there- 
fore it has one hundred times the electric pressure, or 
voltage. Thus by conglomeration of numerous small 
moisture drops into large raindrops the electric pressure 
or voltage of the drop rises until it is high enough so that 
the air cannot hold it back, and it jumps to the next rain- 
drop, and to the next and next, gathering in force by col- 



48 RADIOTELEPHONY 

lecting the electricity of the numerous raindrops, until a 
powerful lightning flash is formed, which passes through 
the cloud until it reaches regions where there are so few 
raindrops, or so little electricity on them that the light- 
ning flash again decreases and gradually fades out. 

"Thus lightning is an electric discharge within the 
cloud, and very rarely does such a lightning flash, when 
reaching the lower edge of the cloud, gather so much 
energy as to enable it to jump the gap from the clouds to 
the ground and to ' strike. ' In other words, only a small 
percentage of the lightning discharges are between cloud 
and ground ; most of them are harmless fireworks within 
the cloud and very pretty to look at. 

"Now whenever a lightning flashes in the cloud or from 
cloud to ground, it sends out an electric wave, and when 
such electric wave reaches an electric circuit, a transmis- 
sion line, etc., it produces a miniature lightning discharge 
in this circuit, by what we call electric induction. If the 
electric pressure or voltage of this induced lightning in 
our electric circuit is high enough, it breaks down the in- 
sulation and shuts down the circuit and 'the lights go 
out. ' Therefor, we have to install lightning arresters in 
all electric circuits to protect them against this induced 
lightning. 

POWER OF LIGHTNING. 

' ' From the action of the induced lightning in our electric 
circuit we can calculate its voltage, and from the voltage 
of this induced lightning in our circuits, which was pro- 
duced by the electric wave sent out by the lightning flash 
in the clouds, we can calculate back the voltage or electric 
pressure of this lightning flash in the clouds, and find 
that the voltage of the lightning flash averages about fifty 
million volts. It may be as low as twenty millions, or 
may go as high as one hundred million volts, and even 




Copyright, International 
ONE INCH SQUARE RADIO SET 
Alfred Giovanni, a fourteen-year-old freshman in the United High 
School at Knoxville, Pa., with his one inch square radio receiving 
instrument, probably the smallest of its kind in the world. The instru- 
ment is capable of picking up radio messages for a distance of more 
than fifteen miles, and is complete in every detail. 




Copyright, International 

RECEIVING CROP REPORTS BY WIRELESS 
No science in recent years has had such strides as has the science 
of radio. The Chicago Board of Trade has just inaugurated a system of 
broadcasting market reports for the information of farmers and those 
interested in the production and marketing of America's foodstuffs. The 
photo shows Charles Daugherty, who is a farmer in Champaign, 111. 
receiving crop reports by the radio way. 



MIRACLE OF THE AGE 49 

higher in the interior of very large thunderclouds. In a 
big lightning flash the current may be some ten thousands 
of amperes. But it lasts only a very short time, one ten- 
thousandths ' of a second or less. Therefore, the power of 
the lightning flash is enormous, from hundreds to thou- 
sands of millions of horsepower, many times larger than 
that of Niagara. But it lasts only such a very short time, 
less than one ten-thousandths ' of a second, so that its 
energy is very small, less than that of a pint of gasoline. 
The destructiveness of lightning, therefore, is not due to 
its great energy, but that its energy is let loose all at once, 
in an extremely short time, just as a pound of dynamite is 
more destructive than a pint of gasoline, though the pint 
of gasoline contains more energy.* ' 

"WHAT IS ETHER?" 

But to return to our major subject the radio, most 
people imagine that ' ' ether ' ' is the atmosphere or a com- 
ponent part thereof. But this is not what the technicians 
say. The term is used to designate the medium used by 
radio energy to pass from its initiative or point of origin 
out into the world and home again. And it is one of the 
startling things that the average person does not pre- 
tend to understand, that the ether may mean air, water or 
a solid body and that these same waves starting out on 
their course do not stop on their way, but pass through 
what we call solid bodies — even human bodies — if they 
happen to be in their way. 

They pass through the room in which you may be sit- 
ting and through your own body, and you can pick them 
up in your own home and without going out of doors by 
using a "loop" to feel the waves, instead of an ordinary 
aerial or antenna, though they may not be quite as strong 
in the room as they might be out in the open. It is be- 
cause of this that anywhere in range of a broadcasting 
4 



50 KADIOTELEPHONY 

station with the proper sort of a receiving set one may 
" listen in" and be answered, entertained or interested. 

One of the highly interesting things that broadcasting 
has given the conntry is a true service. The great gov- 
ernment station at Arlington sends out every morning 
at 11 : 55 and every night at 9 : 55 the correct time, and 
every broadcasting station pauses to tick off the seconds 
so that watches and clocks may be adjusted to official 
time. 

The method of doing this is quite interesting. At 9 : 55 
p. m. the wireless station sends out on a wave length of 
2,500 meters a series of signals. Every tick of the stand- 
ard clock in the Naval Observatory, Washington, is trans- 
mitted as a dot, omitting the twenty-ninth second of each 
minute, the last five seconds of the first four minutes and 
finally the last ten seconds of the last minute, after this 
ten seconds pause there is a dash which is promptly on 
the hour of 10 p. m. and 12 noon. Amateurs all over the 
East tune in for this and wait to tick off the seconds, and 
all along the Atlantic Coast wireless operators on vessels 
pick up the time and set the " ship's clock" accordingly. 



CHAPTER V. 

Scientists and Wizards Who Helped Develop the Wire- 
less — Marconi — Edison — Fleming — DeForest — Squier — 
Poulsen — Alexanderson — Steinmetz. 

UNLIKE most great discoveries or marvelous patents 
which have proved a boon to mankind the credit for 
bringing the radio to its present high state of effi- 
ciency and usefulness cannot properly be credited to any 
one of the great men in the field of science or electricity. 

A number of great principles are involved and applied 
in assembling of an adequate radio set and the discovery 
of one principle has been followed by another until a 
complete scheme of transmitting and receiving wireless 
messages has been built up. 

It was Michael Faraday, an Englishman, who first dis- 
covered magneto-electric induction in 1831. Long before 
much was known about electric waves he found that a cur- 
rent of electricity in one wire can make an electric current 
flow in another wire some distance away — or induce the 
other current, but he did not know about the medium 
through which the electromagnetic effect was produced. 
James Clerk Maxwell, a Scotch physicist, was the one 
who reached the conclusion that the medium by which or 
through which the electromagnetic effect was trans- 
mitted in Faraday's experiments was the " ether.' ' This 
was nearly half a century ago. 

But Maxwell only advanced a theory and proved it to a 
point of scientific acceptance without practical demon- 
stration. It remained for Heinrich Hertz, a German pro- 
fessor, to invent a "sparker" or means by which he could 

51 



52 RADIOTELEPHONY 

see the electromagnetic waves. He created a miniature 
flash of lightning in laboratory, making the electric waves 
radiate from a spark-gap, and because he first devised a 
means of seeing these waves, which travel at the rate of 
186,000 miles a second they became known in the realm of 
science as Hertzian waves — the waves which now trans- 
mit signals or speech in the radio. 

WHAT THE WORLD OWES MARCONI. 

It was Guglielmo Marconi, a twenty-year-old Italian 
boy, who first actually used the waves to transmit signals 
or messages. Marconi, one of the most picturesque fig- 
ures in the wireless world, was born in Bologna, Italy, in 
1874 and attended the University of Bologna where under 
the direction of one of the professors he became inter- 
ested in and began experimenting with electric waves, and 
in 1894 he succeeded in signaling a few hundred feet. 

He devised a wireless telegraph but could not interest 
the Italian government in his scheme and went to Eng- 
land where he made successful tests for the British Postal 
authorities between Penarth and Wiston. His work was 
approved by Sir William Preece, of the English Tele- 
graph System, who however limited its application. 
However, as a result of Marconi's demonstrations the 
Marconi Wireless Company, Ltd., was formed and in 
1899 he had wireless stations on opposite sides of the 
great English Channel, and in 1901 had succeeded in sig- 
naling across the Atlantic from Cornwall to New Found- 
land and a little later from Poldhu to Nova Scotia. 

In the meantime he had demonstrated his ability to 
maintain communication with vessels at sea and suc- 
ceeded in signaling the steamship Philadelphia a distance 
of 2,000 miles from his station and to actually transmit 
messages to it when 1,500 miles out at sea. By 1903 he 



MIRACLE OF THE AGE 53 

had established wireless communication between London 
and New York and within a short time transatlantic steam- 
ships were printing daily morning newspapers containing 
news received by wireless. By 1907 his system had de- 
veloped to a point where a limited commercial wireless 
service was established between London and New York. 

In the development of his projects Marconi invented 
the first electrolytic detector — used to detect the sound 
waves. He called it a " coherer.' ' It was a tube filled 
with iron filings which was affected by the wave oscilla- 
tions. It was, of course, neither so efficient nor sensitive 
as the modern detectors, required frequent readjustment 
and was much slower — so slow in fact that but fifteen or 
twenty words a minute could be received by the wireless 
telegraph operator. 

The advancement of Marconi's wireless in England, it 
might be mentioned incidentally, aroused some antagon- 
ism and there was a near sensation when charges were 
brought that the then Premier Asquith and Chancellor 
Lloyd George had corruptly favored the Marconi Co. 

MARCONI'S WORK IN THE WAR. 

During the war Sig. Marconi returned to Italy and took 
command of the government wireless service. His work 
was recognized in civilized countries everywhere and he 
received many honors. A degree was conferred upon him 
by Glasgow in 1904 and in 1907 he won the Nobel prize in 
physics. In 1914 he was awarded the British A.C.V.A. 
and in 1915 made Senator of the Kingdom of Italy. 

In the development of radio it is somewhat startling to 
find that Thomas A. Edison, the great electrical wizard, 
has had little to do with the actual perfecting of the art 
though many of the things he discovered have been ap- 
plied. It was Edison, for instance, who first discovered 



54: KADIOTELEPHONY 

one of the facts or principles of electro activity that has 
been used in and makes effective the electron tube so es- 
sential to radio communication — particularly radioteleph- 
ony. Long before radio was discovered Edison in his 
experiments with the incandescent lamp which he discov- 
ered and invented, found that when a small metal plate 
was mounted in an incandescent bulb beside the light film, 
and the current of electricity was turned on the electricity 
leaped from the heated film across space to the metal 
plate. The significant thing about this was that when the 
film was connected with the negative pole of a battery and 
the plate with the positive, the current leaped the space 
between the film and plate but when the connection was 
made with the positive attached to the film and the nega- 
tive to the plate there was no flow. In other words he 
discovered the principle of what might be termed the one- 
way valve as applied to the flow of electric currents. But 
Edison made no use of his find. The result he produced 
became known in the electrical world as the ' * Edison Ef - 
feet," but it was not until scientists reached the fixed 
conclusion that everything in the world is composed of 
electrons and that an electric current is simply the flow- 
ing of a stream of electrons that the nature and value of 
what Edison discovered — the Edison effect — was made 
apparent. 

THE FLOW OF ELECTRONS. 

Hot objects emit electrons. The film in an electric 
lamp being white hot it emits electrons which are small 
particles of negative electricity. And since they are nega- 
tive they flow toward the cold positively charged non- 
heated metal plate in the vacuum bulb, because the elec- 
tron principle is that in two negatively charged bodies 
the electrons repel — do not flow — and in two positively 
charged they are practically in the same relation, but 



MIEACLE OF THE AGE 55 

when one is positively charged and the other negatively 
charged the electrons will flow from one to the other — 
from the negative bodies. 

Mr. Edison was born in Milan, 0., in 1847, and though 
it is not generally known began his career as a telegraph 
operator. Early in his life his parents moved to Port 
Hnron, Mich., where he was a newsboy and published a 
small weekly newspaper. 

He became interested in qualitative analysis and fixed 
up a laboratory in an old baggage car, where during an 
experiment with phosphorus he set fire to the car and 
destroyed his small newspaper plant. 

He then took up telegraphy and the study of electricity, 
acting in the meantime as an itinerant operator. Follow- 
ing the lines of the telegraph he finally found his way to 
New Orleans where he made one of his earliest patents — 
an automatic repeater, later developing the duplex and 
vibratory telegraph. 

THE "WIZARD OF MENLO PARK." 

About 1872 he became superintendent of a telegraph 
company in New York and invented the "printing tele- 
graph' J for recording stock quotations, which he sold for 
$40,000. Shortly thereafter he opened his first experi- 
mental laboratory at Menlo Park, N. J., and began the 
development of electric devices and apparatus which 
marked him the most prolific and ingenious man of the 
age. He gave to the world the incandescent lamp, now 
used the world over, and the first phonograph, the patent 
rights for which he sold for $1,000,000. 

His first phonograph was exhibited at the Paris Ex- 
position where a feature was a display of "electric light- 
ing/ ' He gave a similar exposition at the Crystal Palace 
in London in 1885. About this time he removed his 



56 KADIOTELEPHONY 

laboratory to Llewellyn, N. J., constructing the largest at 
that time private laboratory in the world. He also organ- 
ized the Edison General Electric Company with $12,000,- 
000 capital. In 1906 he established a village in Edison, 
N. J., a centre of iron ore deposits and invented a mag- 
netic separator to remove the ore from the rock. 

It has been stated that there are on record in the patent 
office at Washington, D. C, more than 700 patents taken 
out in the great inventor's name. Among these were the 
duplex and quadruplex telegraph which made possible the 
sending of several messages in both directions over a 
single wire at one time ; the autographic, harmonic, mul- 
tiplex, automatic and photo flex telegraph; the Edison 
dynamo, Edison microphone, incandescent lamps, elec- 
tric pen, Edison mimeograph, Edison-Sims torpedo boat, 
telephone transmitter, telephonograph, kinetoscope, vito- 
scope and flourescope, the phonograph, dictaphone and 
electric ore separator. 

"EDISON EFFECT" INSPIRED SCIENTISTS. 

While "the Edison effect' ' discovered by the great in- 
ventor was never used by him Prof. J. A. Fleming, en- 
gaged by Marconi after he formed his English company, 
saw possibilities in it and first utilized it to create what 
he termed an oscillation valve or "flap valve" to detect 
wireless waves — technically a rectifier. It only permitted 
the waves to flow in one direction and suppressed half of 
the oscillations. Fleming applied the idea for the first 
time in radio communication and took the first big step 
toward solving the wireless telephone problem. 

After Fleming came Dr. Lee De Forest, who added the 
improvement to the oscillating valve or vacuum tube, 
which has come to be known as the Aladdin's lamp of the 
electric world. 

Dr. De Forest, who was born at Council Bluffs, la., in 



MIRACLE OF THE AGE 57 

1873 and was educated at Sheffield Scientific School, Yale, 
went to Chicago and was employed in the experimental 
laboratory of the Western Electric Company, about 1899. 
There he became interested in wireless telegraphy and 
began experimenting with a new type of electrolytic de- 
tector. While on this work he mounted a grid of wire 
between the filament and plate in the electron tube such 
as Edison had devised and Fleming developed. This grid 
was attached to a battery and he noted that the slightest 
change in the current to the grid powerfully affected the 
current that passed from the filament to the plate. The 
scheme provided a marvelously sensitive method of con- 
trolling the current received. He invented a device which 
would not only detect the exceedingly weak currents that 
oscillate back and forth in the receiving antenna but a tele- 
phone receiver that would respond more readily than with 
the Fleming oscillating valve. He called his valve the 
"Audion" which is the great amplifier — the wonder of 
the age, which by multiplied use — by installation in series 
can so magnify sensitive waves that the ticking of a watch 
sounds in the ears like the blows of a hammer and the 
walking of a fly becomes audible to human ears. Later it 
was discovered that the "Audion" could be used as an 
alternating current generator. By changing the size of 
the "grid" in the tube any desired frequency — alterna- 
tions of current could be secured, and an expensive ele- 
ment of transmitting — the installation of high frequency 
generators or dynamos was eliminated in part for send- 
ing. 

THE "WIRED WIRELESS." 

Another picturesque American figure in the radio field 
is Major-General George 0. Squier. As head of the 
United States Signal Corps, he originated the "wired 
wireless" the principles of which are referred to else- 



58 KADIOTELEPHONY 

where. During the World War the Signal Corps had 
difficulty in getting necessary braiding machines for mak- 
ing or finishing insulated wire. There was wire and cot- 
ton thread but not enough machines. All the machines in 
the United States could not supply braided covering for 
more than 10,000 miles of twisted pair insulated wire in a 
year and the Corps wanted about 100,000 miles a month. 
It could not be had. 

General Squier tried the use of electron tubes. He sunk 
a bare copper wire in the Potomac river opposite the war 
college. A standard Signal Corps radiotelephone and 
telegraph set was connected to each end of the wire — one 
set to serve as transmitter and the other as a receiver. 
At the receiving end the wire was connected to the "grid" 
terminal of an electron tube. The wire was tuned to a 
high frequency and it developed that excellent telephony 
and telegraphy was obtained. The waves followed the 
wire — not through it. Subsequent tests were made with 
buried wires and wires in the open air — all of which 
proved successful and assured the "wired wireless." 

General Squier was born at Dryden, Mich., in 1865 and 
was graduated from West Point in 1887. He was as- 
signed to the Third Artillery, U. S. Army as second lieu- 
tenant and commissioned a captain of the Signal Corps, 
United States Army in 1901. He was made a major in 
1903 and commander of the cableship Burnside during the 
laying of the Philippine cable-telegraph system in 1902. 
He became chief signal officer of the army in 1917, with 
rank of Brigadier-General and appointed Major-General, 
Signal Corps, U. S. A. in the latter part of the same year. 
He was representative of the War Department and tech- 
nical adviser to the American delegation at the Interna- 
tional Conference on Electrical Communications in Wash- 
ington in 1920, also the State Department at the sessions 



MIRACLE OF THE AGE 59 

of the Provincial Technical Committee of International 
Conference on Electrical Communications in Paris in the 
following year. 

During the war he organized the Aid and Signal Serv- 
ice of the United States Army and was decorated with the 
insignia of the Order of Knight Commander of St. 
Michael and St. George by Field Marshal Sir Douglas 
Haig, at London, in September, 1919. He also was 
awarded the Italian decoration Com. of the Order of the 
Crown, and the Distinguished Service Medal of the United 
States Army, and twice Franklin Institute awarded him 
medals for contributions to science as related to telephony 
and telegraphy. 

One less well known, perhaps, than some of the other ex- 
perts in the radio field is Dr. Valdemar Poulsen, of Den- 
mark. 

RADIOED MUSIC IN 1906. 

Dr. Poulsen was one of the first to experiment with 
radiotelephony ; he used his arc as a source of continuous 
waves and devised several means of modulating the out- 
put. He particularly raised the arc to the status of a 
practically operative generator of radio frequency energy 
by placing the entire arc in an atmosphere of hydrogen, 
or a hydrocarbon vapor, using a carbon electrode for the 
negative side and a copper anode for the positive side. 
He also improved the functioning of the arc. 

In 1906, he established radiophone communications 
over a distance of 600 feet using antenna only fifteen feet 
high. In 1907, with a regular equipment, communication 
was established between Esbjerg and Lyngby, a distance 
of 170 miles. The antenna height was 200 feet, the wave 
length 1,200 meters and the antenna power 300 watts. A 
little later, phonograph music sent from Lyngby was 
heard in Berlin, a distance of about 300 miles, although 



60 EADIOTELEPHONY 

the modulating system did not allow the whole output to 
be modulated. 

Dr. Poulsen 's researches along the radio line were 
especially on continuous wave transmission and recep- 
tion. He designed a system of radiotelegraphy and teleph- 
ony using arcs burning in different gases as a source of 
high frequency oscillations and succeeded in developing a 
practical system, which was used in commercial stations. 

Dr. Poulsen was born in Copenhagen, Denmark, No- 
vember 23, 1869. He studied at the University of Copen- 
hagen and entered the Technical Department of the 
Copenhagen Telephone Co., where for a number of years 
he sperintended the electrical testing operations. He 
colaborated with Professor Pedersen for many years and 
carried on extensive researches in telephony and teleg- 
raphy. He was a member of the Board of the Telegra- 
fonen, Ltd. (Poulsen Patent), from 1902 to 1916 and the 
Poulsen Wireless Telephone and Telegraph Co., U. S. A., 
from 1909 to 1911. 

EXPERT HIGHLY HONORED. 

Dr. Poulsen holds the medal for merit in gold, with 
crown. He is a fellow of the Danish Society of Science 
and he received, in 1900, the Grand Prix of the Interna- 
tional Exhibit in Paris. He was official reporter at the 
International Congress of Electric Applications in To- 
rino, Italy, in 1911, and at Copenhagen in 1912. Dr. Poul- 
sen is a member of the American Institute of Eadio 
Engineers. 

Ernst F. W. Alexander son, consulting engineer of the 
General Electric Company and chief engineer of the 
Radio Corporation of America, is another whose accom- 
plishments in the field of wireless have placed him among 
the foremost in this line. 



MIRACLE OF THE AGE 61 

Mr. Alexanderson was born at Upsala, Sweden, Jan. 
25, 1878, the son of a university professor, A. M. Alex- 
anderson, and Mrs. Amelie von Heidenstam Alexander- 
son. He was graduated from the high school of Lund in 
1896, and afterward studied a year at the University of 
Lund. He then entered the Royal Institute of Technol- 
ogy, Stockholm. This was followed by post-graduate 
work at the Koenigliche Technische Hochschule, Berlin. 

Recognizing that greater opportunities for advance- 
ment of young electrical engineers were to be found in 
America, he came to the United States in 1901 and his 
first position was as electrical draftsman with the C. & C. 
Electric Company of New Jersey. In 1902, he accepted 
employment with the General Electric Company in Sche- 
nectady. He soon became a consulting engineer of the 
company. In November, 1919, he was appointed chief 
engineer for the Radio Corporation of America, the com- 
pany combining the radio interests of the General Elec- 
tric Company and the Marconi Wireless Telegraph 
Company of America. 

Mr. Alexander son's radio researches have greatly ex- 
tended the efficiency of radio transmitting apparatus as 
well as radio receiving apparatus. During the World 
War, he evolved a system of radio reception which has 
become the foundation of the modern "directive method 
of radio reception." The immediate object of this receiv- 
ing system, first known as the barrage receiver, was to 
eliminate malicious radio interference of the enemy, who 
might send out waves of the same or nearly the same 
wave length as those which it was desired to receive. 

Through an ingenious combination of receiving aerial 
systems and special apparatus, he was not only enabled 
to eliminate such interference, but also to receive signals 
from European stations nearby to a high-power transmit- 



62 KADIOTELEPHONY 

ting station in the United States, which operated on the 
same wave length as that of the signal being received. 

One of his developments consisted in the evolution of a 
complete duplex radiotelephone system by which a sub- 
scriber to a land line telephone could establish connection 
with a radiotelephone station and conduct a two-way con- 
versation with the facility of an ordinary land-line circuit. 
Among other things he created a type of high frequency 
alternator especially efficient for radio transmission. 

One of those who have done much in the field of practice 
for radio, but who never got into the great lime-light is 
Michael I. Pupin, head of the Electro Mechanical Depart- 
being sold to the Westinghouse Co. 

Dr. Charles P. Steinmetz, of the General Electric Com- 
pany, one of the stellar figures in the electrical world was 
born in Breslau, Germany, in 1865. He was educated at 
Breslau, Zurich and Berlin, specializing in mathematics, 
electrical engineering and chemistry. He became con- 
sulting engineer of the General Electric Company in 1903 
and was Professor of Electro-physics at Union Univer- 
sity. He has written voluminously on electrical subjects 
and his technical and scientific works are regarded as 
standard. Degrees of honor have been conferred upon 
him by numerous colleges and universities— among them 
Harvard and Union and he is Past President of the 
American Institute of Electrical Engineers and the Il- 
luminating Engineering Society. 



CHAPTER VI. 

Sound Waves — Amplifiers — Condensers — The Vacuum 

Tube and the Part it Plays — Alternating and Direct 

Impulses. 

THE great round world on which we live is sur- 
rounded to a depth of many miles with a substance 
which for want of a better term we designate "at- 
niosimere." Imagine, if you can, a perfect condition of 
nothingness — in other words, a vacuum. Then fill that 
vacuum with particles of oxygen, nitrogen, helium and 
other gases. There you have the atmosphere. Radio 
engineers call this "nothingness" the ether. To this 
ether it is possible to impart a wave motion similar to 
that which occurs in water. 

You know what happens when you hurl a rock into a 
still body of water. The same sort of thing takes place in 
the ether. To transmit radio signals it is necessary to 
first create waves of varying groups and in varying 
strengths and then to intercept these waves (at the de- 
sired receiving end) with apparatus capable of changing 
them to sound waves. 

The actual creation of the waves takes place by the 
forming of an electrical pressure between two surfaces 
separated by a distance of from ten to several hundred 
feet. This electrical pressure is directed toward first one 
and then the other of these two surfaces, the change of 
direction taking place several hundreds of thousands of 
times each second. In common practice the ground is 
used as one surface and the other surface is provided by 
erecting a structure composed of one or two wires, in- 
sulated from the earth and suspended a good many feet 

63 



64 RADIOTELEPHONY 

above it. Between these surfaces an electrical pressure 
of from one to twenty thousand volts is created. (All 
electrical terms denned in subsequent chapters.) This 
starts waves radiating out in all directions. 

These pressure waves are, however, only a part of the 
radio wave. Any wire through which electrical current 
is flowed creates what is known as electromagnetic waves 
and it is the combination of electrostatic waves with these 
electromagnetic w T aves that creates the radio waves. The 
amperes of current put into the antennae correspond to 
the size of the rock that we just hurled into our imaginary 
pool and the volts of electrical pressure correspond to the 
force with which the rock was hurled. The larger the 
rock and the bigger the boy who throws it the greater the 
waves. Just so it is with the radio waves. The more 
amperes of current flowing in the antenna circuit and the 
greater the pressure between antenna and ground, then 
the stronger the waves that are radiated. 

RADIO SOUND WAVES. 

Eadio waves are very similar to sound waves. If you 
strike ' ' C ' ' on the piano the sound waves vibrate 256 
times per second, and either a "C" tuning fork or a wire 
tuned to i i C ' ' and in the immediate vicinity will vibrate 
256 times per second, also. These two wires are tech- 
nically described as being in resonance. Just so the radio 
waves have a definite number of vibrations per second 
and in order to hear a certain station the receiving equip- 
ment must be put in resonance with the waves radiated 
by the transmitter. This is properly called tuning. 

An electrical current changing its direction of flow is 
known as an alterating current. The frequency with 
which it changes its direction gives it its nomenclature. 
By high frequency is meant a current which changes its 




XL 

H 

J 

5 
o 
% 
o 

H 
P 

<tj 

ft 

O 

o 

5 
< 

o H 

<D 
'O 

c 
P 



bc.S 
- u 



c ^ 
3-m 

O (H 

o 

B- 

be 
o to 

l| 

n i 




Copyright, Underwood & Underwood, N. T. 

USING RADIO TO DIRECT MILITARY MOVEMENTS 
Orders are given in the office of the Lane Technical High School of 
Chicago and conducted through a receiving set to the field and there relayed 
to the officer of the field through means of a megaphone. 




►I 

w 

m 



II 



3.C 



g °~ 

kH o g 

CO citL 

6 5jh 

&D M £ 2 

■a <; o o 

o £ o 






5 « 
H 5 






x i v 1 




\ 1 


■J! i-**.' . 


i 





c 



la 

W be 
O "-3 c 

° Q s? „ 



§c 



■0 


d 


O 


; O 


O 


Ph^ 


TS 


. & 




+-» & 


P 


rcjy 


c^ 


£* 


n 


C2 


o 


"- 1 o 


£ 


o« 






MIRACLE OF THE AGE 65 

direction of travel in the wire from several thousand to 
several million times each second. The continuous wave 
transmission seems to be the popular mode, as differen- 
tiating from what is known as the spark type of transmis- 
sion. 

Vacuum tubes of large size are used to generate con- 
tinuous waves and also modulated continuous waves. By 
means of these tubes there is created a vibration of cur- 
rent in a circuit in which there are a coil and an instru- 
ment called a condenser. The coil of wire provides what 
is known as inductance and the condenser provides ca- 
pacity, these two factors being necessary to a vibrating 
circuit. The condenser invariably is made up of brass, 
aluminum, copper or tinfoil separated by sheets of in- 
sulating material known as mica — or by air. Between 
these sheets of metal there is created a static pressure 
similar to that generated in the antenna circuit. To con- 
trol the vibrations of this circuit and, in turn, the waves 
radiated from the antennae ground circuit, we employ 
either a key or a microphone transmitter into which one 
talks. This transmitter takes the human voice. 

SIMPLE DEVICES WORK WONDERS. 

A radio equipment for transmitting consists of four 
principal parts; vacuum tubes, inductance coils, con- 
densers and either a key or a microphone. These are the 
essentials and, in addition, there must be numerous con- 
trols of current, controls of the tubes and controls of the 
vibrations. 

For receiving, four essential parts may be listed — coils, 
for inductance, condensers, for capacity (to tune), a "de- 
tector" and telephone receivers. The human ear is not 
responsive to vibrations of a rate higher than a few thou- 
sand per second. The detector changes the high fre- 



66 EADIOTELEPHONY 

quency waves to impulses traveling in one direction in the 
circuit to the number of from one hundred to a few thou- 
sand per second. Two types of detectors are used — one 
the crystal and the other the audion or vacuum tube de- 
tector. Certain minerals permit current to pass in one 
direction but not in another. Such minerals (galena, 
silicon, and carborundum) are ideal for radio work. 

THE "ALADDIN LAMP" OF RADIO. 

The vacuum tube is one of the best advances on radio 
work. It is one of the most sensitive instruments known 
to modern science and yet it may be handled with good re- 
sults by the amateur. It consists of a glass bulb, similar 
in shape to an electric light bulb, evacuated to a high 
degree and containing three elements — the filament, the 
plate and the grid. The filament is a piece of high-resist- 
ance wire which is heated to brilliancy by current, just as 
is the case in the electric light. This heated filament 
throws off millions of little electrical units known as nega- 
tive ions. Around the filament is constructed a small 
sheet of metal (the plate) to which the ions go, and so 
return to the circuit. These ions can travel only from the 
hot filament to the comparatively cold plate and cannot 
reverse and go in the opposite direction. Thus, the radio 
waves are changed to direct impulses. The grid is in- 
serted to control the number of ions which pass from the 
filament to the plate. This grid is a closely wound spiral 
or a finely woven screen of wire surrounding the filament 
and through which the ions must pass to reach the plate. 
Interposed in the path from filament to plate, any elec- 
trical change put upon it from the antenna circuit will 
either increase or decrease the ions reaching the plate 
and so vary the current through the head receivers. The 
vacuum tube is used also to amplify signal strength. A 



MIRACLE OF THE AGE 67 

tube, when properly connected, will not change the form 
of signals passing through it but will add current, from a 
battery connected in one of the circuits, to the signals, 
making them much louder when passed through head re- 
ceivers or a loud speaking horn. 

The vacuum tube is used in yet another way, for trans- 
mitting. In receiving we change the incoming high fre- 
quency current to direct current. For transmitting, we 
reverse the procedure and use large tubes to change 350, 
500, 1,000 or 2,000 volts direct current into alternating 
current, vibrating at rapid frequencies of 50,000 to 2,000,- 
000 per second. 

One of the great fundamentals in putting together a 
receiving equipment is to remember that each additional 
part added means additional loss of current. Do not sac- 
rifice energy for flexibility of control. Simple receiving 
sets should be easier to handle and less apt to get out of 
order. 

The instruments necessary for receiving radio may 
either be purchased individually by the amateur who 
wishes to experiment with various combinations and 
hook-ups, or they can be bought in handsome cabinets 
with antennas and ground equipment, ready to be put into 
operation. Great strides are being made in the production 
of complete equipments and in various parts used in con- 
junction with the receiving of radio impulses. In fact, so 
rapid are these strides that at the moment of writing it 
were difficult to suggest any single equipment or type of 
equipment that would be more desirable or effective from 
any angle than others that constantly are being brought 
forward. It is well to reiterate, however, that the simpler 
the equipment the more efficient it will be found to be and 
the least costly in the long run. 



CHAPTEE VII. 

Electricity — What is it 1 — Electrons — Atoms — Matter 

and its Component Parts — The Valve Theory — What 

Has Made Wireless Telephony Possible ? 

WITHOUT doubt the most wonderful single force— 
or is it actually a combination of forces ? — that has 
been given to man for his use is that of electricity. 
But what is electricity? That is a question that dates 
back to the first experiments made by Ben Franklin with 
his little silken kite and his brass key and silk thread, and 
his little collecting jar. The progress that has been made 
since then in the development of this most wonderful of 
God-given forces is more than miraculous but who shall 
say what the end will be ? Surely, in electricity man has 
the greatest possibility for future development, both me- 
chanically and theoretically. Much that is inexplicable 
even to scientists today may one day be an open book, 
through the agent of electricity. Who can tell 1 

Today we are nearer than ever to an exact knowledge 
concerning electricity. Scientists believe that the whole 
world, including the table from which you eat your daily 
bread, the bed upon which you take your rest, your own 
body — all are composed of what they have called "elec- 
trons." Electricity is also measured in or composed of 
electrons. Therefore, electricity and matter cannot be 
easily differentiated. First we have the molecule as a 
measure of matter. It of itself is unbelievably small and 
so small in fact as to be almost beyond the comprehension 
of the average individual. But then there is the atom, of 
which the molecule is composed. And this unit, the atom, 
is more than infinitesimal in its proportions. But even 

68 



MIRACLE OF THE AGE 69 

beyond this smallest of small units we find the electron. 
For instance, an atom of gold is like a solar system. It 
consists of a central nucleus, like our sun, around which 
revolve electrons, much as if they were planets. 

Each atom of matter — be it copper or rubber or water 
— has so many electrons and no more. Just so long as it 
contains its proper number of electrons it is possessed of 
no electrical effect. That is why the table from which 
you take your meals, or the bed upon which you take your 
rest, seem to exert no electrical action — and the same ap- 
plies to your own body, except under abnormal conditions. 
But, take away from any one substance a portion of its 
electrons or give to it more than its proper share and im- 
mediately you begin to see electrical action. If a body 
contains fewer electrons than it properly should have, 
then it is said to be positively charged. If it contains 
more than its proper number then it is said to be nega- 
tively charged. The plus sign is used to designate bodies 
that are positively charged and the negative, or minus 
sign, to designate bodies that are negatively charged. 

WHAT BATTERIES AND DYNAMOS DO. 

The battery and the dynamo are but elaborations of 
this broad principle. They contain ability to push elec- 
trons out at their negative pole or exit while at the same 
time taking electrons in at their positive pole or entrance. 
The thing we term electrical current is nothing more nor 
less than floiv of electrons in a definite circuit, such as a 
wire or conductor of any sort. When an electric spark is 
"jumped" or flashed across from one terminal to another 
— bridging a gap — the electrons surge back and forth, 
trying to distribute themselves so that there shall be no 
more on one side of the gap than on the other. So long 
as the equation is unbalanced and one side has more than 



70 EADIOTELEPHONY 

the other the electrons continue with their work of trying 
to balance things, and keep leaping across the gap. The 
rapidity and momentum of their flow gives them a certain 
impetus which means that even after they have bridged 
the gap in sufficient numbers to balance the equation they 
still continue to bridge the gap and cross over in numbers 
larger than is necessary to reestablish equilibrium. This 
surging back and forth continues for an almost imper- 
ceptible part of a second and does not cease until each side 
has exactly the same number of electrons. 

The electron theory just outlined is the fundamental 
underlying principle upon which the actual mechanics of 
the radiotelephone are based. Probably the outstanding 
keynote of the principle of the wireless telephone is the 
vacuum tube, which frequently is called the electron tube. 
Thus we clearly see the importance of a grasp of this all- 
important electron theory if wireless telephony is to be 
properly understood and correctly applied. 

EDISON'S DISCOVERY PRECEDED HERTZ. 

Certain it is that the miracles of wireless telephony 
cannot be traced to any one definite thing any more clearly 
than to the perfection of the vacuum tube. You are fa- 
miliar with the incandescent light bulb. In other words, 
you know what makes the glow of an electric light — a fila- 
ment heated to white heat in a glass enclosure which has 
been exhausted of its oxygen content — or nearly so, there 
being no such thing as a perfect vacuum. 

For the better part of a generation this filament glowed 
and glowed and no one suspected that it performed any 
more useful or definite function than to shed light. Edi- 
son's first classic experient with the filament bulb was 
conducted before Hertz made his experimentation. Edi- 
son took an incandescent bulb and mounted a small plate 



MIRACLE OF THE AGE 71 

near to the filament. The plate was put in so that it did 
not come into direct contact with the filament. It formed 
part of a local circuit of its own, in which a galvanometer, 
or current indicator, was included. 

The current was turned on and the filament made to 
glow. Then a curious phenomenon took place. Despite 
the fact that there was no physical contact between the 
filament and the plate the galvanometer needle was seen 
to be deflected. This proved clearly that electric current 
had leaped over the gap between the plate and the fila- 
ment. This was dubbed by scientists the ' * Edison effect. ' J 
It went without explanation for perhaps twenty years. 

WHAT IS AN ELECTRIC CURRENT? 

Then came the discovery of X-rays and radio-activity. 
It was not until scientists reached the conclusion that all 
matter is composed of electrons and that electric current 
is nothing more nor less than a steady flow of electrons 
that a satisfactory solution of the "Edison effect' ' was 
reached. 

Hot objects emit electrons. A filament in a lamp is 
white hot and it therefore emits electrons. Electrons may 
be called infinitesimal particles of negative electricity. 
Their tendency is to flow constantly toward a cold, posi- 
tively charged plate or piece of metal. Two negatively 
charged bodies repel each other. Two bodies charged op- 
positely (one positive and one negative) have attraction 
for each other. No reason for this could be assigned until 
the electron theory was formulated. 

Excess electrons from one body try to supply the lack 
of electrons in another body. Two bodies that are nega- 
tively charged contain an excess of electrons and there- 
fore there is no need of more in either body. Hence, there 
is no physical attraction. Two bodies that are positively 



72 EADIOTELEPHONY 

charged contain each a deficiency of electrons. Therefore 
they repel each other, much like a pair of jealous children, 
each afraid that the other will attempt to take from it its 
own supply of candy or what not. But when excess elec- 
trons have a chance to flow from a body which is nega- 
tively charged to a body which is positively charged (the 
latter therefore being in need of electrons), then there is 
presented the phenomenon of attraction. Thus we get the 
fundamental underlying principle of the vacuum incan- 
descent lamp. 

HOT BODIES THROW OFF ELECTRONS. 

Hot bodies are constantly expelling or exuding elec- 
trons. Why, therefore, has their function, their presence, 
their properties not been discovered before ? Because the 
atmosphere acts as a check or absorber and stops their 
flow. The absence of air from the incandescent bulb 
makes it possible for the electrons to leap across the gap 
between the filament and the plate. If the air were not 
expelled the electron, being so very, very much smaller 
than the atom, is physically checked just as a stone is 
checked in its flight if hurled up against a blank stonewall. 
These electrons are excess and leap from the red-hot fila- 
ment as they are pumped through it with the ever-flowing 
electric current. 

Professor J. A. Fleming has done a great deal toward 
the perfection of wireless telephony and making it a 
workable principle. He was engaged originally by Mar- 
coni as chief engineer, soon after Marconi organized his 
English company. Fleming saw the possibilities in the 
thing that Edison had discovered. Here was a container 
in which a steady stream of electrons could be induced, 
always flowing in one direction, passing from the hot to 
the "cold" plate. These electrons could not flow back 
whence they came. Here, it seemed to Fleming, was a 



MIRACLE OF THE AGE 73 

possibility for the working out of a physical means of re- 
ceiving messages without the aid of wires intervening 
between the point of origin and the point of reception of 
the message. 

In those days telegraph signals were still sent by sparks 
instead of by arcs or dynamos. The oscillations that con- 
stitute a spark come in groups or trains, corresponding 
with a spark. There may be from 50 to 500 sparks per 
second. Hence we find from 50 to 500 radiated wave 
groups, each of which in turn may contain from 20 to 100 
oscillations or waves. Between alternations or changes 
of direction in flow of the current in the oscillations or 
waves there may be only about one-millionth or half- 
millionth part of a second. The human ear is capable of 
absorbing not more than 32,000 vibrations per second. 
The telephone diaphragm responds to more, but the hu- 
man ear will not absorb them from the telephone dia- 
phragm. Even the telephone diaphragm has a limit 
which is well short of several hundred thousand a second, 
the number of vibrations used in transmitting wireless 
wave impulses. 

"EDISON EFFECT" USED IN FLAP VALVE. 

Now, suppose that these movements of electricity were 
transferred into one steady stream, all in one direction. 
Gushes would be received at the spark frequency of about 
50 to 100 per second and would be heard and distinguisha- 
ble in a telephone. 

And now we come to Fleming's development. 

He knew that there were certain valves called "flap 
valves' ' that prevent water or gas in a pipe or main from 
flowing back again in the direction from whence it came. 
These flap valves are capable of opening in only one di- 
rection. Fleming desired just this sort of a thing for 



74 KADIOTELEPHONY 

electricity. At this stage his attention was directed to the 
Edison development, known as the "Edison effect," 
whereby electric impulses were passed from the hot fila- 
ment to the cold plate and did not return, maintaining a 
stream in one direction. If this filament and plate formed 
part of a telephone circuit the receiver at his ear would be 
affected by impulses flowing in only one direction. Hence, 
the rapid oscillations of electrons were converted into 
gushes of electricity, passing all in one direction through 
the telephone. These gushes came at intervals of from 50 
to 100 per second and therefore were discernible to the 
human ear. The plate was charged first negatively and 
then positively as the waves came in. When it was 
charged positively the electrons flowed over to it from the 
filament and when it was negatively charged there was no 
stream at all. Thus, half the oscillations were sup- 

THE OSCILLATING VALVE. 

So long as a radio signal was coming in there would be 
a one-way current through the tube and through any ap- 
paratus connected directly in series (continuously in line) 
with the tube. Half the vibrations were suppressed and 
therefore the diaphragm of the telephone receiver could 
respond and this it did in the form of a high-pitched 
musical note instead of in the form of clicks. The clicks 
are received at the rate of about five hundred a second 
when the transmitting station uses a spark. Fleming 
called his valve an oscillating valve, because it acted like 
a "flap valve" to permit the passage of current in one 
direction only. This suppression of oscillation of an al- 
ternating current is called rectification. 

The extraordinary sensitiveness of the oscillating valve 
immediately won a place for itself as a receiver in long- 
distance telegraphy. The advance made by radio as a re- 



MIRACLE OF THE AGE 75 

suit of this invention was truly remarkable. Then on the 
heels of the Fleming valve came the improvement of Lee 
De Forest, known as the "Auction." 

De Forest inserted between the filament and the plate a 
grid connected with a battery. H$ found that the slight- 
est change in the current to the grid powerfully affected 
the current that passed from the filament to the plate. 
Thus, he perfected a marvelously sensitive method of 
control of the impulses. The grid serves as a control 
throttle and chokes down the oscillations or impulses just 
as the throttle valve of a locomotive chokes down the flow 
of live steam to the piston. It takes a very slight pull of 
the locomotive throttle to release against the driving rod 
a tremendous amount of energy and thus set in motion a 
heavy and inert train of fully-laden freight cars. De 
Forest perfected a device which not only would detect the 
exceedingly weak currents that oscillate back and forth 
in an antenna but also cause the telephone receiver to 
respond more markedly than was possible with the oscil- 
lation valve perfected by Fleming. 

EFFECT AMPLIFIED TEN TRILLION TIMES. 

The effect picked up by one oscillation can be magnified 
by a second valve and the combined effect of the second 
magnified by the third and the third by a fourth and so 
on. Valve can be piled upon valve until the original effect 
is amplified as much as ten trillion times, if that proves 
necessary. To give a concrete idea of what that would 
mean the walking of a fly across a ceiling magnified ten 
trillion times would become a tremendous volume of 
sound. The ticking of a watch, thus magnified, would be- 
come as a boiler foundry. When we say "amplification" 
in radio we merely mean magnification. It takes but little 
current to set up a flow of electrons from the hot filament 



76 RADIOTELEPHONY 

to the plate. This may be accomplished by a small stor- 
age battery or by a few cells. 

In modern vacuum or electron tubes the filament is 
surrounded by a sheath-like grid and a sheath-like plate. 
The electrons are shot out in all directions in every in- 
candescent lamp that is constructed of the so-called vacu- 
um type. The introduction of an electrified plate causes 
the electrons to flow toward it. The battery current gives 
them speed and direction, literally pulling them across, 
if that figure may be used. 

It is the vacuum valve that has made possible the won- 
derful things that already have been accomplished with 
wireless telephony. For instance, it now is possible to 
call San Francisco on the telephone from New York and 
it is the vacuum valve that has enabled us to combine 
wireless telephoning with wire telephoning. It is not a 
far distant flight of fancy to picture a man comfortably 
esconced at his desk in his library easy chair talking over 
the wireless telephone, from Chicago to London. Within 
a very short time it is entirely probable that all the fast 
liners and limited trains will be equipped with wireless 
sets, for the receiving of radiotelephone messages. 



CHAPTER VIII. 

What Air Really Is — Atmospheric Pressure and How it 

"Was Discovered — Three Forms of Matter — Molecular 

Attraction — How Big is a Molecule? — Moisture in the 

Air — Measure of Humidity. 

WITHOUT shadow of doubt the greatest agent of 
power, the most wonderfully plastic and limitless 
fund of energy that yet has been worked upon by 
scientists of all ages is Electricity. And of course elec- 
tricity is the agent which has made radio possible. The 
possibilities of this most remarkable of all sources of 
energy (or is it more properly described as energy it- 
self?) are staggering. Think of the progress that has 
been made in the last few dozen years in development of 
electrical man-aids and then cast the picture a score of 
years ahead and it is most difficult to reason out just 
what may be brought forth. Certain it is that this state- 
ment rings true: — electricity has given mankind more 
in the way of real progress and development than has 
perhaps any one other agent as yet discovered. 

Right here it might be well to take to pieces to some ex- 
tent the findings of the scientists and the course of reason- 
ing they follow in leading up to their discoveries and 
formulae After all, expressed in terms a little more 
readily understandable by the average person, there is 
no more delightfully interesting story than that of elec- 
tricity as it is known to scientists of today. 

First of all, we must consider Matter. There are 
three different states of matter — solid, liquid and gas. 
Different bodies may possess different properties even 

77 



78 BADIOTELEPHONY 

though they be made of the same substance or kind of 
matter. As we are accustomed to think of it, iron is a 
much harder substance than wood. And yet iron may be 
drawn into fine wire or rolled into thin plates. x\nd the 
iron-wire mattress certainly is more comfortably to sleep 
on than is the hard woden plank. By certain treatment 
iron may be reduced to a porous, spongy condition. It 
may be melted and if it is heated beyond the melting 
point it becomes a gas. Iron is known to exist in the sun 
in gaseous form. Think of the many different forms of 
this one material, iron, and yet it is fundamentally the 
same in each case, no matter what form it has been led 
into. Here a fairly fine distinction must be drawn. The 
changes that we have described as taking place in iron are 
what are properly classified as physical changes and come 
under the laws of Physics or Natural Philosophy. We 
may place a bar of iron in the open, moist air and it will 
begin to rust almost at once. That rust that appears on 
the surface of the iron is in no sense a physical phenome- 
non and the change does not come under the head of laws 
of Physics but rather under the realm of Chemistry. 

THE THREE FORMS OF MATTER. 

Think for a moment of water. Here we have a sub- 
stance which can exist in three distinct forms : — ice, water 
and vapor — solid, liquid, and gas. It is a substance which 
can take on three different forms and which in each of 
these three different forms performs very differently. 
Ice can be cut. It has definite shape and can be handled. 
Water cannot and it offers very little resistance to a 
shearing stress. Water, vapor, or steam, cannot be 
handled and has no permanent volume or shape. A solid 
has a definite mass, volume and shape and it opposes any 
stress. We have, however, two classes of solids — rigid 



MIRACLE OF THE AGE 79 

and elastic. A perfectly rigid solid retains its shape 
permanently no matter what stress is brought npon it. 
A perfectly elastic solid regains its original shape in spite 
of any stress. All bodies can be divided np into very 
small particles. Gold, for instance, can be hammered out 
until 300,000 leaves of it are only an inch thick. Platinnm 
wire 1-3,000,000 of an inch in diameter has been drawn. 
Then, we have powdered chalk, used largely for polish- 
ing. If powdered chalk be mixed with water and the 
larger particles allowed to settle, the cloudy liquid being 
poured off, this cloudy liquid will evaporate and leave 
behind it an extremely fine powder. So very fine is this 
powder that it cannot be perceived by touch. And yet 
if metal is polished with it, it is found to leave behind it 
on the metal very fine marks, showing conclusively that 
the particles of the powder are possessed of a very de- 
finite shape though they are of such very extraordinary 
minuteness. 

HOW SMALL ARE PARTICLES OF MATTER. 

Back in 1823 Leslie advanced the statement that a 
single grain of musk had been known to perfume a room 
for the space of twenty years. He estimated that "this 
single grain of musk contained 320 quadrillions of par- 
ticles. ' ' There must be a limit to the extent to which this 
subdivision can be carried. Apparently that limit is the 
human ability to comprehend and measure the minute- 
ness of the particle after the matter has been subdivided. 

If we consider again the very smallest particle of mat- 
ter—the gold leaf, the fine platinum wire, the grain of 
precipitated chalk — it must invariably have a definite 
shape. Its molecules cling together. That is true in the 
caso of solids. In the case of gases, however, the mole- 
cules behave differently. They will expand and fill any 



80 RADIOTELEPHONY 

space, no matter how great the space, opening as they do 
so the distance between themselves. This is what is 
meant by rarefied air. And, incidentally, it is the real 
reason why no snch thing as an absolutely true vacuum 
is possible. Molecules in turn are formed of atoms com- 
bined in definite proportions. A molecule of water is 
always a molecule of water no matter whether the sub- 
stance takes the form of water or steam or ice. 

MOLECULES CONSTANTLY IN MOTION. 

Even with the aid of the most powerful of microscopes 
a cube whose side is the 4,000th of a millimeter mav be 
taken as the minimum visible for observers of the present 
day. A cube of this sort would contain froin\60,000,000 
to 100,000,000 molecules of oxygen and nitrogen. The 
best microscopes can be made to magnify from 6,000 to 
8,000 times. A microscope which would take that result 
and magnify it as much again would show the molecular 
structure of water. For instance, if a globe of water the 
size of a football (6 1-4 in.) in diameter were magnified 
to the size of the earth the molecules or granules would 
be hardly greater than small shot and certainly less than 
footballs in size. If we magnify a cubic inch of water to 
a cube whose side is the diameter of the earth, in the 
enormously magnified cube there will be one particle to 
every cubic inch. 

The action of molecular constituents of a gas is well 
to note at this point. In a gas no force is needed to sepa- 
rate the molecules from one another. The molecules are 
in motion constantly. And the same applies to the mole- 
cules of all bodies. This is what is known as molecular 
motion. In a gas the molecules rush hither and thither, 
colliding with one another and with the sides of the con- 
taining vessel. In the atmosphere the number of col- 




Copyright, Underwood & Underwood, N. Y. 
NEW COM 1 'ACT RADIO DEVICE CARRIED IN SUITCASE 
Brent Daniel, of Washington, is here shown with his supersensitive 
radio receiving device, so compact that it can be carried in an ordinary 
suitcase. The new radio device is capable of receiving messages within 
a radius of 400 miles. This radio set was one of the most prominent 
exhibits at the Radio Convention held in Washington. 



^I'^rhT^ 





.., 1 ^t,^^....^-..,*f 




Copyright, Underwood & Underwood, N. Y. 
THE WORLD'S LARGEST RADIO STATION ON LONG ISLAND 
Photo shows the powerhouse and cooling pond at "Radio Central" — 
the world's largest wireless station — plant of the Radio Corporation of 
America, at Rocky Point, near Port Jefferson, L. I. 



MIRACLE OF THE AGE 81 

lisions per second between particles is infinite and a mole- 
cule travels on an average 1,000 times its own diameter 
without colliding with another. If the air be rarefied the 
collisions of necessity become less frequent. It is inter- 
esting to note in passing that scientists have estimated 
that in an incandescent bulb, the air being so rarefied as 
to be nearly as possible a perfect vacuum, the free path 
of a molecule, or the distance it will travel without collid- 
ing with another, is about 35 feet. 

MOLECULAR ATTRACTION. 

Thus we have an idealized picture of infinite simally 
small particles rushing madly about in the very substance 
of which they are a component part, colliding with one 
another, simply through reason of their mutual attrac- 
tion. Experiments made with an idea of determining at 
what distance molecular attraction is felt show that their 
influence has been detected through a film of silver two- 
millionths of an inch thick. What application has all this 
to practical consideration of every-day facts and oc- 
currences! Simply this: Substances such as steel get 
their high tensile strength from the force of the attrac- 
tion of the molecules which go to make it up. In a sub- 
stance such as steel, where the tensile strength is as high 
as 30 tons per square inch, the molecular attraction can 
be seen to be remarkably high. On the other hand, in 
liquids, the molecular forces are relatively small. In a 
gas at ordinary pressure there is practically no molecular 
attraction. 

Just in passing it might be of interest to illustrate how 

this law of molecular force acts in the case of solids. Two 

balls, one of glass and one of steel, are allowed to fall 

upon a smooth steel plate which has been slightly greased. 

After their impact it is found that well-defined circles 
6 



82 KADIOTELEPHONY 

have been left on the surface of the steel plate, proving 
that the balls were compressed. That they recovered 
their original shape is proof of their elasticity and of the 
action of their molecules. The exactness to which science 
has been developed may be emphasized at this point by 
remarking that in the case of the glass and steel balls it 
is perfectly possible to photograph and measure their 
momentary distortion. 

The pressure of the atmosphere is the most widely ex- 
tended of all fluid pressure and yet its existence was not 
suspected by the early philosophers and its discovery 
has a personal history. Certain effects of atmospheric 
pressure had been noted but their cause had not been 
correctly assigned. For instance, the fact that water will 
rise in a pump, following the plunger, was held to show 
that "nature abhors a vacuum.' ' In 1642 the philosopher 
Galileo was appealed to for an explanation of the failure 
of certain pumps which were erected in the gardens of 
the Duke of Tuscany. They were designed to draw water 
from a depth of 50 feet. The water would rise about 
thirty feet but no higher. Apparently, there was a limit 
to which the "abhorence of Nature' ' would go. Galileo 
evidently indicated to his pupil Torricelli the probable 
explanation but he died without having been able to 
prove it. Torricelli took up the question. He argued 
that if a column of water would rise to a height of about 
30 feet, mercury, being 13 1-2 times as heavy, must rise to 
a height of about 27 inches. The Torricellian experiment 
was the result. Here we have a glass tube closed at one 
end and filled with mercury. This tube is inverted in a 
basin of the same substance. The mercury sinks in the 
tube until the column is about 30 inches above the sur- 
face of the mercury in the basin. What holds that column 
of mercury, apparently unsupported? In what way did 



MIRACLE OF THE AGE 83 

the surface of the mercury inside the tube differ from 
the surface of the mercury outside of it? Only in one 
feature — there was no air in contact with it. Then, it 
must be the pressure of the air to which the support of 
the column of mercury is due. Then along came Pascal. 
He took the Torricellian tube to varying heights and he 
found that the length of the column of mercury supported 
by the atmosphere decreased as he ascended. In 1648 he 
made two observations. One of these was at the bottom 
of Puy de Dome and the other at the top, a height of 
3,565 feet. At the bottom the mercury column stood 27 
inches and at the top it had fallen to 24.7 inches. As he 
came down again he saw the mercury gradually rise in 
the tube until it was the same height as formerly. Thus, 
in a space of six years, three men, all following one after 
another and upon the death of the other, worked out one 
of the most important principals of natural philosophy. 
And from that time on the belief was abandoned that 
* ' Nature abhors a vacuum. ' ' 

ATMOSPHERIC PRESSURE AFFECTS RADIO. 

This subject of atmospheric pressure has a very great 
bearing upon radiotelephony. It may be seen at a glance 
just why this is so. If a series of waves, broadcasted 
through the ether at a certain pressure, strike high and 
low spots, or in other words, places where the atmospheric 
pressure is greater or less, then compensation for this dif- 
ference must be made and the general result is a tendency 
toward interference. Many refinements of the radio 
doubtless will be made to take care of this as well as to 
get around the element of temperature (the receiving of 
impulses being more difficult upon hot, sticky nights than 
at other times). Refinements of this sort will have to fol- 
low along with many other improvements which will regu- 



84 EADIOTELEPHONY 

late the sending and receiving to bring both to more and 
more of an exact science. 

We might well say that the universal pressure of the 
atmosphere was utilized long before it really was known 
to exist. When a boy uses a " sucker' ' he calls in the aid 
of atmospheric pressure. A piece of leather is thorough- 
ly softened in water and a piece of string is attached 
firmly to the middle of the leather. It will fit closely on 
a stone or any smooth object. When the string is pulled 
a vacuum is created underneath and the atmospheric 
pressure presses the edges firmly against the stone, mak- 
ing them adhere sufficiently for the string to lift the stone. 
The limit to the force that can be applied is the product 
of the atmospheric pressure and the area of the leather, 
for this is the force which the pressure of the air exerts 
to make the stone follow the " sucker/ ' 

ATMOSPHERIC MOISTURE. 

The weather often affords a topic of conversation in 
our variable climate because of the way in which its 
changes influence our life. The warmth or cold, the dry- 
ness or dampness of the atmosphere affect our feelings 
and our health so much that they attract our attention. 
That there always is a considerable amount of water in 
the atmosphere is shown by the simplest of experiments. 
The moisture condensed on a tumbler of cold water is evi- 
dence that there is water in the air which cannot be seen. 
If a saucer containing sulphuric acid is left open to the 
air it imbibes moisture from the air and therefore in- 
creases in weight. Both sulphuric acid and calcium 
chloride possess this property of absorbing moisture 
from the air. Thus, they can be used to absorb all the 
water from air which is closely adjacent to them. The 
density of water vapor in the air is called the humidity. 



MIRACLE OF THE AGE 85 

It varies from one grain per cubic foot on a cold day to 
ten grains per cubic foot on a day of tropical beat and 
dampness. It is a common remark to make, "The air is 
very dry, ' ' when water evaporates freely. Consequently, 
on sucb a day clothes dry rapidly. We call the air dry 
when it is far from saturation and call it damp when it 
is nearly saturated. The relative humidity and the dry- 
ing power of the air are numerical estimates of what our 
senses feel as to the dampness and dryness of the air. 

The water vapor in the air exerts a pressure which de- 
pends upon its quantity and on the temperature. If the 
air become warmer and the vapor pressure remain the 
same the vapor expands and becomes less; the same oc- 
curs if the temperature remains the same and the vapor 
pressure decreases. In either case, the amount of water 
vapor in the cubic foot is decreased and the air becomes 
1 ' unsaturated. ' ' The vapor pressure is then not the max- 
imum for that temperature or, in other words, it is the 
maximum pressure for a temperature below that of the 
air. The dew point is the temperature at which dew is 
formed. The dew point depends upon the prevalent 
pressure of water vapor alone. If the dew point and the 
temperature are known, the amount of water vapor in the 
air can be ascertained. All of this has its own peculiar 
effect upon radio transmission and influences the extend- 
ing ether waves and our ability to detect them. 



CHAPTEK IX. 

Radiation — Radiant Energy — Intensity of Radiation — 

Reflection — Refraction — Diathermancy — Obscure Rays 

— Absorption — Radiation and Absorption — Distribution 

of Radiant Energy. 

HOW many of us ever really stop to consider why 
there is a difference between day and night ? Do 
we not, most of us, go along from week to week 
and month to month taking for granted the wonderful 
workings of Nature just as we find them! What, after 
all, gives us light? The sun, of course. Its rays pass 
through millions of miles of intervening space and finally 
register themselves upon our optic mechanism. But the 
sun functions in another way to provide us with a neces- 
sary quantity. It furnishes us with heat. Some light 
rays, such as moonlight, impart no perceptible heat. On 
the other hand, there are heat waves which can be felt at 
some distance from the emanating object (as in the case 
of a stove, etc.) and yet there is no visible radiation. Heat 
is transmitted through a distance by radiation. 

Here it is that we have the underlying thought of 
radio — radiation. The fundamentals underlying the ra- 
diation of heat are the same as those from which the radio 
has been developed. Eadiation of heat is the transmis- 
sion of heat from a hotter to a colder body by means of 
vibrations of the luminiferous ether. Here the laws of 
light and heat overlap each other, the principle of trans- 
mission of radiant heat being the same as those of trans- 
mission of light. 

Were we to be a bit technical for the moment it might 
be said that radiation is defined as the transmission of 

86 



MIRACLE OF THE AGE 87 

heat energy through a medium, but without heating that 
medium. In this case, by " medium' ' is meant the ether 
through which the heat waves are transmitted. The term 
"medium" here actually applies to the intervening sub- 
stance — gas, vapor, liquid or solid, which always is heated 
more or less by radiation through it. The transmission 
of heat also is accomplished by what is known as induc- 
tion. Here a warmer particle comes into contact with a 
colder particle and transmission of heat takes place. 
Through radiation, however, the temperature of the in- 
tervening substance does not come into the question. An 
analogy might be drawn here, with the radiation rep- 
resenting the new wireless telephone and induction rep- 
resenting the older and perhaps better-known wired sys- 
tem. 

RADIATION OF LIGHT AND HEAT WAVES. 

In radiation of light or heat waves, heat energy is 
transformed at the surface of the radiating body into 
energy of vibration of the luminiferous ether, which is 
again transformed into light or heat on meeting some 
other body, but which upon the way is not what ordinarily 
may be termed either light or heat. From a source of 
light there proceed also rays which do not cause light 
but which produce heating effects. These rays are tech- 
nically known as "obscure" rays and to detect them and 
measure their intensity the "thermopile" issued. 

In order to prove that both heat and light rays proceed 
in straight lines the following experiment was worked 
out by scientists. An upright stand is provided and a 
heated ball placed on it. Also there is provided a double 
heat screen which has a square hole through it. On the 
other side, and at an equal distance, there is placed a 
plain screen. Now, if a candle be placed on the stand so 
that its flame occupies the same position the heated ball 



88 EADIOTELEPHONY 

will occupy, a square of light is traced on the plain 
screen, proving that the rays of light proceed in straight 
lines through the hole. Then the ball is heated and placed 
on the stand. The eye no longer can detect any rays but 
if a thermopile be brought to the place where the square of 
light was seen on the plain screen the thermopile instant- 
ly registers an effect, while at other places there is no 
efT ect. This shows that the * ' obscure ' ' heat rays as well 
as the light rays proceed in straight lines. 

In experiments of this sort, in order to intercept radia- 
tion, a double screen is used. This consists of two paral- 
lel sheets or plates of tin or wood standing vertically, 
with a space between them for the circulation of air. The 
plate nearer to the source of heat may become heated but 
the currents passing up between the two plates carry 
away the heat and prevent any heating of the further 
plate. This, therefore, does not receive any of the radi- 
ant heat from the source and the radiant heat is inter- 
cepted entirely. 

We all know what it is to scorch one 's shins before an 
open fire. It is dangerous to get too close to a fire. The 
intensity of radiant heat diminishes with the distance 
from the source of heat. The ratio at which this diminu- 
tion takes place is an exact law. Suppose that the hole 
in the double screen be exactly one inch square and that 
this screen be placed halfway between the further screen 
and a candle. The patch of light on the further screen is 
exactly four inches square or in other words four times 
the area of the hole. The energy passing through the 
square inch at the hole has, in double the distance, spread 
itself over the four square inches. Kadiation in every 
case is a wave motion, as will be explained in greater de- 
tail later. 

In the earlier days when roasting meat before an open 



MIRACLE OF THE AG& 89 

fire was done more frequently than perhaps now is the 
case it was the custom to place a bright tin screen around 
the meat to reflect the rays of heat back onto it. The laws 
of radiation of heat are exactly the same as those of ra- 
diation of light. The rays in each case are cast in straight 
lines (known technically as rectilinear propagation), and 
the reflection of each is the same. 

LIGHT RAYS AND HEAT:. 

We all can remember back to boyhood days and the use 
of the burning glass. We all remember having glowed 
over fiction (and in some cases true) stories of how 
marooned sailors have maintained life and heat by kin- 
dling fire through concentrated heat obtained by the use 
of a watch crystal filled with water, to focus the light 
rays and concentrate them upon a given point. But very 
recently the police department of a certain city was 
puzzled by repeated occurrences of fire in a certain dwel- 
ling. Invariably the fire was started in the living room 
and almost without exception the carpet and hangings 
were badly damaged. After repetition three or four 
times it finally was discovered that a globe filled with 
water, for goldfish, was acting as a " burning glass' ' and 
focusing the light rays down upon one definite spot with 
such force that conflagration took place. This principal 
has been highly developed and used by scientists in exact 
recording work. The instrument in mind is known as 
Campbell's Sunshine Recorder. It consists of a glass 
ball which concentrates the rays of the sun onto a card- 
board, on which the principal focus of the sphere falls. 
So long as the sun is shining it leaves a trace of charred 
paper. Later work with this instrument proved that the 
glass absorbed much of the heat which fell upon it so that 
it was not a suitable material with which to experiment 



90 EADIOTELEPHONY 

on infraction, as this branch of Physics is known. Still, 
these two examples serve to show that heat radiation is 
refracted under certain conditions and that in this respect 
they behave in much the same manner as does light. 

Diathermancy is literally the capacity of any given body 
for transmitting radiant heat. Experiments conducted 
by Melloni proved that solids vary widely in their capac- 
ity for transmitting radiant heat. For instance, the fol- 
lowing substances are listed in the order of their relative 
diathermancy: — rocksalt, sulphur, iceland spar, glass, 
gum, alum, sugar. 

To test the diathermancy of liquids a thin glass cell for 
holding the liquid is used. By using this it is seen that 
water intercepts the " obscure' ' rays from the source of 
radiation, though, like glass, it is clear and transparent to 
light rays. On the other hand, carbon disulphide trans- 
mits the invisible heat rays freely. 

And now we come to the diathermancy of gases, which 
perhaps is the keynote of the particular branch of Physics 
we have been just considering as far as its application to 
radio is concerned. In all the experiments mentioned 
thus far it has been assumed that the radiation passes 
through the air without hindrance. Dry air and the per- 
manent gases transmit radiation, from whatever source 
of heat, without hindrance, and behave practically as a 
vacuum as far as the transmission of rays of heat is con- 
cerned. Vapors, however, vary very much in their dia- 
thermancy among one another and with the nature of the 
source of radiation. 

The water vapor surrounding the earth forms a screen, 
which tempers the rays of the sun and also prevents the 
heat of the earth from radiating into space. Kegarding 
the earth as a source of heat, at least ten per cent of the 
radiation from it is intercepted within ten feet of the 



MIRACLE OF THE AGE 91 

ground. The amount of vapor present in the air is vary- 
ing continuously. Even on a clear night the cooling of 
the earth's surface by radiation is checked by the vapor- 
screen which surrounds it. In the same way the rays of 
the sun are tempered by our vapor-screen. Mountaineers 
suffer very intensely from their heat. The quantity of 
vapor diminishes very rapidly as they ascend and on a 
mountainside the pressure of water vapor may be very 
small. In such cases the sun's rays are almost intoler- 
able. Explorers and mountain climbers frequently com- 
plain bitterly of the oppression of the heat. A graphic 
story has been recounted by an acquaintance of the edi- 
tor's who says that in climbing Mont Blanc, though he 
was at many points in snow up to his waist, the sun 
blazed against him with almost unendurable force. Mar- 
iners frequently have reported that they have seen the 
pitch in the seams of a vessel boiling while the air about 
the ship was below the freezing point. The early morn- 
ing in the summer generally is the time of least humidity 
and the scorching heat of the sun then is very evident. 
The paint on doors which face eastward often is blistered 
by the untempered rays of the morning sun, though the 
temperature of the air may be very moderate. 

The sun's rays, before they reach the earth, have to 
pass through our vapor-laden atmosphere and this cuts 
off a great deal of the obscure radiation. However, in 
the solar spectrum the heating effect of the obscure rays 
is twice that of the visible rays. The spectrum of the 
solar beam, analyzed at the high observatories, where the 
vapor layer is much thinner, shows a much greater pro- 
portion of obscure rays. 

Professor Langley's bolometer aids in testing the 
presence of radiation of small intensity. It is an instru- 
ment of great delicacy. With its aid the obscure rays 



92 KADIOTELEPHONY 

of the ultra-violet spectrum have been mapped out and 
lines of no radiation detected in the solar beam there, 
similar to the Fraunhofer lines of the visible spectrum. 
Iodine is very opaque to light. It is used, therefore, in 
making a filter which allows the obscure rays of a lumi- 
nous beam to be isolated. Iodine is very diathermous or 
transparent to the obscure rays. By placing a filter of 
iodine before the opening of an electric lamp a beam of 
radiant energy, intensely powerful though quite invisible, 
may be projected and experimented upon. These rays 
are of sufficient power to set paper alight and even to 
raise platinum to the point of incandescence. 

RADIANT HEAT AND RADIANT LIGHT. 

Eadiant heat is identical with radiant light. It differs 
from red light as red differs from blue. Just as different 
substances absorb rays of light from different parts of 
the spectrum and so have different colors, so different 
substances absorb some of the rays of heat which sources 
of heat are radiating, in different proportion. For ex- 
ample, glass transmits heat rays from a lamp to a con- 
siderable extent but none from a copper ball at the tem- 
perature of boiling water, because it is opaque to rays 
from the invisible part of the spectrum. 

Take for instance, the case of greenhouses. Here the 
rays of the sun traverse the glass because they are from 
the luminous part of the spectrum and they heat the solid 
objects in the house, the walls, floor, etc. The obscure 
rays which these heated objects give out cannot penetrate 
the glass, which thus is "a trap to catch a sunbeam.' ' 
Although the air and the permanent gases offer little or 
no obstruction to the passage of the heat rays, vapors as 
well as liquid and solid substances vary in their diather- 
mancy. What happens to the heat rays when they stop ? 



MIRACLE OF THE AGE 93 

They must of course heat the substances which stop 
them. For example, the glass of the greenhouse, al- 
though it permits the luminous portion of the sun's rays 
to pass through, stops obscure rays and becomes very 
hot. 

The transformation of the heat energy into energy of 
vibration of the light-ether takes place at the surface of 
the hot body. As might be supposed, the character, na- 
ture, texture, or "grain" of the surface affects the amount 
of energy which is transformed into vibration. It is a 
well-known fact that radiation takes place slowly from 
bright surfaces. Steam pipes, teapots, hot-water jugs, 
if kept very bright, do not lose heat so quickly as do dull 
surfaces. In everyday work we have become accustomed 
to speaking of radiation in referring to loss of heat from 
the surface of the bodies whereas in more scientific work 
the term is used for the ether vibrations themselves. The 
word absorption is used inversely. That is, it applies to 
the transformation of energy of ether vibration into heat 
energy. This takes place at the surface of the body which 
is being heated by radiation and the grain or texture of 
this surface affects its power of absorbing vibrations in 
the form of heat. A bright body takes up less heat from 
radiation which falls upon it than does a dull body. The 
bright fire irons remain cool for some time after a fire 
has been lighted, whereas a dull fender becomes intensely 
hot. This process is called absorption. Both the radia- 
tion and the absorption of dull bodies is greater than is 
the case with bright bodies. 

In connection with the foregoing, remember that : — 

Good radiators are good absorbers. 

Bad radiators are bad absorbers. 

An experiment which is due to Franklin has led many 
people erroneously to conclude that the color of a sub- 



94 KADIOTELEPHONY 

stance alone influences absorption. Several cloths of 
different color were laid out on the snow in the sunshine 
and as they did not sink at the same rate in the snow 
Franklin concluded that they absorbed heat differently 
because of their difference in color. A red cloth is red 
because it absorbs the green rays and a violet cloth in a 
similar way absorbs the radiation of the heating portion 
of the spectrum. In this way dark clothing becomes hot 
while light clothing reflects much of the sun's rays and re- 
mains cool. So long as radiation consists wholly or chief- 
ly of obscure rays, absorption is independent of color, 
but the sun's rays so far as they come from the luminous 
part of the spectrum, are more absorbed by dark bodies 
than by light ones. 

When the vibrations of the light-ether reach the sur- 
face of a body they are partly reflected and partly ab- 
sorbed, or transformed into heat energy. If the sub- 
stance be diathermous most of them pass on and are re- 
flected back from the inner surface. The part of them 
which is absorbed raises the temperature of the body, 
which then emits radiation in turn. So, then, there are 
only four ways in which radiation falling on a body is 
disposed of and we have these axiomatic statements : — 

Good absorbers are good radiators and bad reflectors. 

Good reflectors are bad absorbers and bacFradiators. 

In diathermous substances more radiant energy is re- 
fracted and less is absorbed and reflected. 

In substances which are the opposite of being diather- 
mous more radiant energy is reflected and absorbed and 
little or none is refracted. The sum of the radiation 
which falls upon the surface must be equal to the total of 
the radiation which enters the substance, whether ab- 
sorbed or refracted, together with that which is reflected. 

All of these fundamental laws form the basis of radio 
work, as will be explained in detail later. 



CHAPTER X. 

Heat Waves — Conduction — Convection — Wave Motions 

— Harmonic Waves — Interference of Waves — Medium 

Necessary to Transmission of Waves — The Ether the 

Medium for Radio Waves. 

HOW often we have heard the common expression, 
' ' How cold it is. The cold in this part of the conn- 
try is very intense.' 9 And yet, do yon realize that 
there is no such thing as coldl Heat is a definite thing, 
but the thing we speak of as "cold" is merely an absence 
of heat. It is common knowledge that heat flows from 
point to point, always from a hotter to a colder point. 
The matter of heat radiation was taken up in chapter 
nine. That is one of the ways in which heat is trans- 
mitted from one point to another. As we stand before a 
fire and spread out our hands to the crackling logs we feel 
the sensation of heat. That heat is transmitted to us by 
radiation. But how about the sensation we get when the 
coffee happens to be too hot and raises a little blister on 
the end of the tongue or when we put our hands into the 
shaving water in the morning? That is the sensation of 
heat. We have felt heat because heat has been trans- 
mitted. But the transmission took place not through 
radiation but through definite contact — and this is what is 
known as conduction. If the water is cooler than the 
hands we place in it, the reverse action takes place and 
the heat is transmitted from the hands to the water, but 
by conduction as in the other case. It may be said in more 
definite language that heat is transmitted by conduction 
when any particle of a body is raised to a higher tem- 
perature owing to its contact with a particle which is 

95 



96 RADIOTELEPHONY 

hotter than itself. But all substances do not conduct heat 
in the same fashion. For instance, if we place a silver 
spoon in a cup of coffee the handle of the spoon becomes 
hot very rapidly. But if that spoon were made of bone 
we would find no sensation of heat transmitted to the 
handle, comparatively speaking. Why is it that house- 
wives for generations have used things they call "iron 
holders"? Because the flat irons with which they finish 
their laundry transmit heat very rapidly up into their 
handles and to grasp the bare handle would be to burn 
the flesh. But a little later an iron with a wooden handle 
which was detachable and fit the irons universally was 
invented and the hot irons now may be picked up and 
used with the iron holder and without danger of burning 
the hands. 

BEARING UPON RADIO. 

All of this has a definite bearing upon radio. Eadio is 
possible through the application of the laws of radiation 
and conduction to the element electricity. The funda- 
mental laws that govern the action of heat and light 
waves actually apply to the radiation of electrical dis- 
turbances. In radio, however, many elements have to 
enter into our problem. For instance, the nature of the 
ether, the tendencies of various metals used in the appli- 
ances, etc. 

In passing it might be well to point to the fact that a 
substance like water is, for instance, a very poor conduc- 
tor of heat. To prove this one can take a long narrow 
test tube (glass) and place in its bottom a piece of ice, 
weighted down with some heavier substance to keep it 
from floating to the top. By applying a flame to the up- 
per part of this test tube the water in this portion of the 
tube may be boiled, the steam or water vapor will carry 




U CO >>0>,C 




S o o« . 


o-t-> > two 


£ c ofi 


d 0> ffl "S 


+3 «jh o — • g 


S wfE^cB 


9- s-6 >■ 


g e wc 

^ _, o 

<» r *- o 


rt^^o 


2°rt ® 




3*3 g§ 


S^S^« 


CS C O+j rj 


+JIUI, "^ 


to 2<h - 

o)« 5 a 


w >S2 lrt 


|g2t"2 


.c a bc+s 


F 9 - d 


0)-" £ M 


-'O'Stl 


^ca) M S 


1«^js2 


o s'S— i^ 


■H 5 Sh M O 


i au 
entic 
are 
aeri 
r. C 




e «»H2 
l>43 w o 


to o 

pt t 

mes 
alls. 
d sh 


O V z> 


C3-£ . o 


OS rt F W)^3 


physici 
men to 

importa 
f makin 
rear. P 


&^°» 


Chica 
ssiona 
tfit ar 
rocess 
in th 
adio. 


first 
profe 
io ou 
the p 
rack 
uto r 


TJ 0) a 


rell, the 
Chicago 
th a ra 
y be in 
the tir 
of his 


+J ._ M o CO 


vid Cot 
among 
pped w 
e he m 
coupe t< 
v mean 






C , o 


•Srt^g-.2 


.Q O P-2.C 




I 4) +-> 

*** 

be ^ 

*£3 



J 01+-' o 
n 02 O 03 

o ^^^ 

8*32 

J ?" 5 

U o m " 

H ^ -g 
£ £ 3> a 
W .2 '43 
fe 5 ^ o 
to S2^ o 

M 05 g <u 
02 2^tf 
P "Y >»^ 

^ O e§ •£ 

co fe^.S o 

M &J)S & O 
02 o> bc+j ro 

2 .§11 

2~gg 

S ^s 




CQ H ra.£ 
c > <t> 

to,c TO qj 
TO 03 — C 

f£H£ 



o 



nj cfl to 
M o to 



v ■ 



V 



^ £ W &- 
<V 03 03 "^ 

Co C 

"•£ W > 

tdvf 

^3- o 



*°£~ 

fiOJOC 
03 <Ur-( O 

,2 TO 02 - 
Jh.C~ 03 

*.£ £ 
££§. 

o> o — 
C 3«o o 

<* - °-2 






c 3 

o ,£ 



TO 



"~ 03 o5 U c 

c a .- 

•<k. TO — 
*j TO *r 

£.50.2 



MIRACLE OF THE AGE 97 

off the tremendous amount of excess heat up and into the 
air and the ice at the bottom remains in its original state 
unmelted. 

CONDUCTION. 

Then, let us for a moment consider this subject of con- 
duction as applied to solids. To prove that different 
solids have different conductivity the following experi- 
ment was evolved. A long copper trough is constructed 
with several short tubes projecting into it near the bot- 
tom. Into these, corks are inserted. Through the middle 
of each cork there is passed a rod of metal, slate, glass or 
other substance, one end of which is projected into the 
trough and the other end allowed to extend about eight 
to ten inches outside. The outer part of each rod is dipped 
in paraffin wax, which melts at 140 degrees F. When 
this wax cools on the rods it forms a solid coating. The 
trough is then filled with oil and heat applied to boil the 
oil. This heat is carried along the different bars by con- 
duction, melting the wax coating to a different extent in 
each case, thus indicating the relative conductivity of the 
metals tested. The wax is seen to melt, probably to the 
end of the copper rod, which proves that copper is an 
excellent conductor of heat. The wax on the brass and 
iron rods melts for a considerable distance but the wax 
on the bone or glass and slate melts for a very short dis- 
tance indeed. On the wooden rod it is melted only so 
much as it is affected by the radiation of heat from the 
sides of the trough itself. Except in the case of the best 
conductors the heat is radiated or carried off by the air 
more easily than conducted by the rod and so the end 
does not reach the melting temperature. 

Did we need any further and more familiar demonstra- 
tion of the application of these physical laws of conduc- 
tion and radiation we might point to the teapot and to 



98 EADIOTELEPHONY 

the woolen "cosy" which the good housewives were wont 
to put over them to keep their heat in. The non-conduct- 
ing properties of animal and vegetable substances are 
put to use in handles of utensils which are exposed to heat 
and in clothing the body with flannel. Why do we wear 
winter underwear? To keep the cold out? No. To keep 
the heat in. Clothing maintains next to the body a layer 
of air which is at the temperature of the body and so 
avoids its cooling by radiation, evaporation or convection. 
Wisps of straw are wound around trees and pipes to keep 
them from freezing. Ice is packed in flannel or sawdust 
to keep the heat away from it. Steam pipes and boilers 
are covered with hair felt and bone meal or asbestos 
packing to keep them from losing heat. Asbestos is a 
fibrous substance and a bad conductor for the same 
reason that furs and feathers keep their owners warm in 
cold weather. The fibers are bad conductors and there 
are interstices between the fibers over which the heat 
does not pass by conduction. Fur or down keeps the heat 
of the body from escaping. A swan or duck will float for 
hours on water little above the freezing point because its 
feathers and down prevent its heat from escaping to the 
cold water. 

Water may be boiled in a paper bag. The heat is con- 
ducted through the bag so that the temperature of the 
paper is never very much above the boiling point. A 
cylinder is built up, half of copper and half of wood. If 
this be wrapped round with paper and held over a lamp 
the paper next the copper remains while that touching 
the wood is burned. The copper, being a good conductor, 
carries off* the heat of the flame and the paper remains 
cool, while the wood leaves the paper to its fate. 

Convection is the transmission of heat from one place 
to another by means of the actual motion of the heated 



MIRACLE OF THE r AGE 99 

particles of a heated fluid. The fluid is heated by conduc- 
tion and becomes lighter so that it rises as a result of its 
expansion and carries the heat off with it. The great 
ocean currents, as well as the steady and variable winds, 
are nothing more nor less than gigantic examples of the 
law of convection. Heat expands or extends in all direc- 
tions, always trying to effect an uniform temperature of 
all surrounding elements. This tendency to effect an 
equilibrium of temperature is going on habitually. 

WAVE MOTION. 

Let us now hark back more definitely to the thought of 
radio in its practical aspects. What makes it possible? 
Wave motion. The electrical disturbances of the ether 
are of the form of wave motions. We are all more than 
familiar with the old parable of the stone and the still 
pond, how the stone dropped into the still pond sets up a 
wave motion and actually a series of waves which widen 
out from the central point where the stone fell. Does 
the water really take part in this apparent motion? Does 
it really move outward from this center? We can decide 
this best by noticing the motion of some stick or leaf upon 
the surface of the pond. As one of the successive circles 
reaches it, it rises and then falls again. But it does not 
move outward with the wavelet. It keeps its old place on 
the pond. This proves to us that the water itself is not 
moving outward from the point where the stone fell, for 
if it were the leaf would move with it. The motion that 
actually takes place is merely each portion of the pond's 
surface is rising and then falling, with perhaps a slight 
motion from side to side. 

Watch a river when the wind is blowing upstream. The 
motion of the little waves will fool you into believing that 
the stream actually is flowing backwards. But observe a 



100 EADIOTELEPHONY 

bubble on the stream and it will be found to be moving 
steadily down stream, rising and falling as it meets each 
wave. A person in a small boat or swimming in the sea 
will notice the motion imparted to the boat, or to himself 
as the case may be, with each successive wave. Imagine 
for a moment that you are in the ocean getting your 
summer coat of tan. Imagine yourself in the trough be- 
tween two wave crests facing the advancing wave. As 
the wave comes, you are carried forward and upward 
until halfway up its face. Then the forward motion 
ceases and a backward and upward motion follows until 
you are on the crest of the wave. The backward motion 
continues until you are halfway down the slope of the re- 
treating wave and you are carried forward again (though 
downward) until you are in the trough once more. No 
doubt you have described something of a circle and your 
movements have been copied by every portion of the sur- 
face of the water in front of you and will be copied by 
every portion of the surface of the water behind you. 
The steady onward movement of the waves is not an ac- 
tual onward movement of the water itself. What we do 
see moving onward is a state of things, a shape, a wave 
form. It is well to bear this law in mind, for on it hangs 
the fundamental principle of radio. The waves propelled 
in radio transmission are not actual movements of matter 
but are merely a form or a state of things. 

You will remember when you were a child what pleas- 
ure you used to get out of nothing more elaborate in the 
way of a plaything than a bit of rope. Stretch that rope 
out on the ground and when you jerk one end of it a wave 
will travel the length of it, caused by each particle of the 
rope transmitting that energy to its neighboring particle. 
Another familiar instance of this is the barley or wheat 
field. With a wind blowing smartly across a field of 



MIRACLE OF THE AGE 101 

grain a beautiful wave motion is provided. Here, how- 
ever, the waves are furnished not by each stalk or ear 
forcing its neighbor down but the successive impacts of 
the air on one stalk or ear after another. 

Here we come then to a fresh consideration. But let us 
always bear in mind that a motion of a state of things 
is distinctly different from a motion of a material body. 
One further example that will clear this difference is the 
motion that follows along the path of a procession or a 
parade. In every procession there is one outstanding 
high light that produces more enthusiasm from the audi- 
ence than any other. As the procession moves along we 
may notice the movement of a disturbance in the crowd, 
first one man cheering and waving his hat, then the man 
next to him, and this state of things traveling along the 
crowd, keeping always parallel, or nearly so, to that 
enthusiasm-producing high point in the parade. Actually 
what takes place is that a wave of excitement travels 
along at the same pace with the carriage or whatever 
be the high point of excitement. We must emphasize 
here that if there were no crowd there would be no wave 
of excitement. If there were no parade there would be no 
wave of excitement. The crowd is the medium through 
which this wave of excitement is carried. In radio the 
ether takes the place of the crowd and the electrical im- 
pulse which sends forth the wave takes the place of the 
parade. 

Remember, then, that heat, light and sound all travel 
by wave motion. In the case of light we have another 
example of wave transmission and since light travels 
from the sun to the earth it follows that interstellar space 
must be filled with some medium capable of transmitting 
the disturbance which, when it affects our eyes, we call 
light. 



102 EADIOTELEPHONY 

We have several forms of wave motion. There is the 
periodic motion. By this we mean the motion which 
brings the oscillating body back to the spot from which 
it started, at regular intervals. The length of the periods 
of time which elapse between the return of the body to 
its original condition is known as the period of the mo- 
tion. Oscillations, vibrations, swings are other names for 
periodic motion. The simplest and most familiar ex- 
ample, perhaps is the pendulum. The phase of a moving 
particle may be defined in simplest possible terms as the 
fraction of a period that has elapsed since it last passed 
through the central point in the positive direction. This 
is well to remember, since phase is a term which figures 
largely in electrical work, especially when we begin the 
consideration of alternating current. And of course ra- 
dio work is possible only with alternating current, since 
that current is the only kind which will effect a disturb- 
ance in the ether. 

HARMONIC WAVES. 

Simple harmonic motion is what the term implies— a 
motion which is as nearly perfectly harmonic as is pos- 
sible under natural conditions. Many times a simple har- 
monic motion is combined with a uniform rectilinear 
motion. An instance of this would be a pendulum swing- 
ing and tracing its path along a board being drawn along 
at a uniform rate of speed under the point of the pen- 
dulum. 

It may be seen at a glance how great are the possibil- 
ities of combination of these motions. We have the 
simple pendulum and the compound pendulum and then 
also we have the various wave forms made possible by 
combination of these with rectilinear motion. If we 
have a system of particles in line at equal distance and 
those particles are a fixed distance ahead of each other 



MIRACLE OF THE AGE 103 

and are put in motion the result is a wave form, a simple 
harmonic curve, which appears to move steadily along. 
If each particle performs one of these composite move- 
ments that we have been considering the wave form will 
be the composite complicated curve resulting and it will 
appear to move steadily along in the direction of the line 
of particles. 

WAVE INTERFERENCE. 

Longitudinal waves of compression and rarefaction, 
transverse vibration, circular waves, primary and second- 
ary waves, plane waves, spherical waves as reflected on 
a plane surface, spherical waves as refracted on a plane 
surf ace — all of these are terms more or less technical, each 
of which describes a definite element entering into the 
science with which we are dealing. It is unnecessary to 
go into their technical ramifications here, however. Their 
very titles indicate to the casual reader their story. How- 
ever, there is one other branch of this very broad sub- 
ject of waves which is worthy of attention and that is in- 
terference of waves. 

Let us go back to that same little pool of water and this 
time let us drop in two stones instead of the proverbial 
one. Let us drop them simultaneously but from different 
points, not very far, however, from each other. We shall 
then have two sets of circles spreading from the two cen- 
ters. What happens when a circle from one center meets 
and crosses a circle from the other? Where the two 
crests meet there is a double elevation of the surface of 
the water and where the two troughs meet there is a 
doubly deep trough. But where the hollow of one wave 
crosses the crest of the other the two opposite forces 
neutralize each other and the surface of the water is 
neither raised nor lowered. Then there is a patchwork 
of crests and hollows and neutral spaces. This principle 



104 EADIOTELEPHONY 

of interference applies to all cases where similar sets of 
waves are sent out from two or more different sources. 
The effect produced at any given point will be the alge- 
braic sum of the effects of each wave separately. 

In cases where waves (of any sort) meet with an ob- 
struction and there is an aperture in that obstruction the 
resulting effect differs depending upon the nature and 
length of the wave. If the wave be long compared with 
the size of the aperture the distance will be transmitted 
obliquely. In this way we account for the transmission 
of sound around the corners. In very small waves (such 
as light waves) the effect of the screen will be to cut off 
the effects of the waves from all points except those op- 
posite the aperture. 

In the next chapter we will take up magnetism, the 
measurement of magnetic forces, the fundamentals of 
electricity and the general foundation upon which radio is 
built. The study of heat and sound and light wave trans- 
mission will be found to have a close parallel to the trans- 
mission of the electrical impulses through the ether, 
which make the radio possible. There are other inter- 
esting things in connection with the general study of 
waves, such as the refraction and reflection of light and 
sound waves, etc., but for the needs of this work the 
fundamental facts that have been given in the foregoing 
chapter will be sufficient for a basic understanding of the 
laws which govern the operation of the radio and all that 
enters into it. 



CHAPTER XI. 

Magnetism — Lodestone — The Compass — Hard and Soft 

Iron — Effect on Nickel, Silver, Gold — How to Make a 

Magnet — Effect of Vibration — Induction — Time Lag — 

Magnetic Dip — Magnetic Fields. 

NO more interesting — and shall we not also say mys- 
tifying'? — phenomenon exists in nature than that of 
magnetism. And, since magnetism is so funda- 
mentally tied up with the underlying principles of elec- 
tricity, and because electricity is the wonderful medium 
which has made the Age Miracle, Radio, possible, it is 
necessary to consider next the many sides of the subject 
of magnetism. 

To everyone the word lodestone is a more or less com- 
mon thing. The lodestone is found in Nature and it ac- 
tually is a natural magnet. Magnets are constructed by 
artificial means but they do exist in Nature in an elemen- 
tal state which is quite capable of attracting bodies. The 
lodestone is literally iron ore found in the form of irregu- 
lar stones, which attract to them and hold or support 
small pieces of steel or iron. To the early Greeks this 
stone was commonly known and was called "magnes," 
from which comes its name or derivative i ' magnet. ' ' The 
stones were found first near Magnesia, in Lydia. Very 
ordinary specimens have been found which were capable 
of supporting a few grains. It is said, however, that that 
most famous of scientists, the man from whom came our 
knowledge of gravity, Sir Isaac Newton, possessed a ring 
containing a lodestone which weighed only three grains 
but which could support a dead weight of more than 
three ounces. The specimen of lodestone which is in 

105 



106 RADIOTELEPHONY 

keeping at the University at Edinburgh will support a 
weight of more than 200 pounds. 

The lodestone, or magnet, as reproduced by man con- 
sists of a piece of hard steel which is rubbed with a lode- 
stone or another magnet (artificial) or magnetized by 
electricity. Usually these artificial magnets are made in 
the form of a horseshoe. You undoubtedly remember in 
your boyhood days of performing all sorts of weird 
" stunts' ' with a concealed magnet. Now, a magnet is a 
peculiar thing. Its two ends differ from each other. 
And either end exerts a much stronger magnetic influence 
than does the middle. To prove this take an artificial 
magnet and dip it into a heap of iron filings or shavings. 
You will find that these iron filings or shavings cluster 
themselves thickly around the edges and ends of the mag- 
net and leave the middle quite free. In other words, the 
extreme end of any magnet exerts the most powerful in- 
fluence of any spot on the magnet. For that reason the 
ends are called poles. 

Mariners chart their way over the trackless seas with 
what is known as a compass. Foresters use the same 
thing. The artillery and other branches of the army use 
the compass for "orienting" themselves, or finding out 
where they are, in relation to the map or in relation to 
other objects. This is possible for the following reason : 
The magnet, if supported so that it can turn horizontally 
with ease, will persistently set itself so that its end points 
toward the North, the other end of course pointing toward 
the South. If you mark that end which points toward the 
North at the first "try," then you will find that same end 
will always swing around toward the North. This is 
due to the effect upon the magnet of the poles of the earth. 
The end which points toward the North is called the 
"North Pole" of the magnet. It is often called the 



MIEACLE OF THE AGE 107 

"North-seeking Pole," "The Marked End" or the "Red 
Pole," since most magnets have the north-seeking pole 
indicated as being such by means of a file mark or by 
being colored red. The practice of coloring the north- 
seeking pole red and the sonth-seeking pole blue was in- 
troduced by Sir G. Airy, a noted astronomer. 

NEWTON'S LAW. 

One of Sir Isaac Newton's most important laws is "To 
every action there is an equal reaction." This you can 
clearly see is the case with the magnet. In no case is 
there a tendency for the magnet to move bodily toward 
either pole. It merely swings on its center until the 
north-seeking pole points to the magnetic north and the 
opposite pole to the magnetic south. When the ends of 
the magnet have properly pointed themselves to their 
respective poles the magnet comes to rest. You can see 
from this that, the red pole being swung around to the 
North and the opposite pole to the South, there is being 
exerted upon the magnet a combination of forces or, as it 
is described in technical language, a "couple." These 
forces that affect the position of the magnet are properly 
termed the Earth's "Directive Couple." When the mag- 
net has been swung about so that it lies due north and 
south that force or couple is exactly zero and the magnet 
comes to rest. Should the magnet be swung around forci- 
bly so that it lies due east and west the Directive Couple 
is then at its maximum power. 

A magnet will act upon a piece of unmagnetized iron 
or steel at all points with equal intensity. For instance, 
the ends and the middle of a bar of unmagnetized iron or 
steel will be attracted with equal intensity. This case is 
different, however, when a magnet is presented to another 
magnet. Then you find that the red pole of one magnet 



108 EADIOTELEPHONY 

attracts the blue pole of the other magnet and vice versa, 
the law being that like poles repel and unlike poles at- 
tract. Whether it be the blue pole repelling the other 
blue pole or whether it be the blue pole of one attracting 
the red pole of the other makes no difference, the result 
being the same and the law that like bodies repel and un- 
like bodies attract holding good in every case. This is 
the law upon which magnetism and, out of it, electricity 
is formulated. 

MOTION IN MAGNETISM. 

Experiments have been devised to prove that repulsion 
does take place, as for instance when a bar magnet is 
slung by means of strings so that it cannot turn and then 
is slowly approached, at its red pole, by the red pole of 
another magnet. The suspended magnet will be repelled 
to a very considerable and visible extent (sometimes as 
much as two or three inches). 

With the possible exception of nickel and cobalt, both 
of which are slightly susceptible to magnetism, iron and 
steel are the only two substances which are attracted by 
magnets with any very considerable force. The relation 
of the magnetism of copper, silver, gold, etc., to that of 
iron is shown by the fact that an electromagnet which 
can lift fourteen pounds of iron cannot lift one grain of 
copper, silver or gold. The experiments conducted 
through a considerable space of time by Faraday show 
that all substances are to some extent affected by magnet- 
ism, either positively or negatively. Some substances are 
to a slight extent repelled by the magnet. Among these 
are bismuth, phosphorus, antimony and zinc. 

Magnetism plays queer pranks occasionally. To show 
its imperviousness to common insulation, it is quite pos- 
sible to pick up a piece of iron or steel by means of a 
magnet acting through a plate of glass or a board or a 



MIRACLE OF THE AGE 109 

brick. Frequently scientists have been bewildered by the 
peculiar actions of the very delicate instruments with 
which they have been at work. Trouble may be caused in 
one room with a very highly sensitive instrument by a 
charwoman carrying iron buckets in another room, or by 
bicycles in a neighboring playground. Frequently diffi- 
culty was experienced in the laboratories of King's Col- 
lege, until at last it was found that the steamers plying 
back and forth on the neighboring Thames river (with 
their steel hulls) were having an effect upon the instru- 
ments. Often a careful experimenter has thoughtfully 
removed from his person all iron or steel articles, such 
as pocketknives, keys, etc., and still found an inexplicable 
deviation in his instruments, which after careful process 
of elimination was traceable to a corset steel of an as- 
sistant, the wire stiffening of a woman's hat or many un- 
usual things. 

MAGNETISM OF METALS. 

A piece of iron or steel placed in contact with or even 
brought near to a magnet becomes itself a magnet. An 
ordinary piece of soft iron ceases to be a magnet imme- 
diately on removal. So does hard iron or steel, providing 
the magnetization has been comparatively feeble. How- 
ever, hard iron or steel, after having been at all strongly 
magnetized, retain their magnetism upon being removed 
from contact with the original magnet and they will in 
turn act upon other pieces of iron or steel. The difference 
between soft iron and hard iron lies chiefly in the fact that 
the former can be filed with comparative ease whereas this 
is not true of the latter. Also, a soft iron becomes mag- 
netized easily and loses its magnetism easily whereas the 
reverse is true of hard iron. The mechanical qualities 
depend in a complex manner, not only on their chemical 
composition, which is to say their percentage of carbon 



110 RADIOTELEPHONY 

and other substances, but also upon the processes of 
hardening, tempering and annealing, and upon the strains 
which they have undergone. The magnetic qualities de- 
pend in an equally complex manner upon these self -same 
conditions. 

It is interesting to note the effect of a magnetized bar 
upon itself. When a bar has been magnetized its own 
poles, being unlike, attract each other and hence they at 
once set up a force which tends to demagnetize the bar. 
Obviously, this tendency will be much greater when the 
poles are brought closer together, as is the case in a short 
bar. If a bar is less in length than fifty times its own 
diameter, or thickness, the demagnetization takes place 
very rapidly. Even when the length is fifty times the 
diameter the magnetism remaining in the bar is only one- 
tenth of that which would remain in a very long rod. 

EFFECT OF TEMPERATURE. 

The effect of vibration upon magnetization is of great 
interest to us, especially as it connects closely with the 
subject of radio. If a bar of annealed soft iron is sub- 
jected to a magnetizing force and is then subjected to 
vibration the magnetization is tremendously multiplied. 
On the other hand, with hard iron or steel, which has been 
magnetized but is separated from its source of magnetiza- 
tion, the act of smartly tapping the bar or rod reduces its 
residual magnetism to an unbelievable extent. 

In magnetization work there is an element which fre- 
quently is spoken of and that is Time Lag. This is noth- 
ing more nor less than a lapse of rapidity of magnetization 
after a certain percentage of the full magnetization has 
been accomplished. On one experiment it was found that 
a piece of soft iron under weak magnetization forces un- 
derwent during the first five seconds an increase of from 



MIRACLE OF THE AGE 111 

30 to 50 per cent of its instantaneous value and then in- 
creased only 20 per cent in the next full minute. In hard 
iron and steel, however, Time Lag is very rarely per- 
ceptible. 

Temperature has a very marked and very interesting 
effect upon magnetism of any given specimen. If the 
temperature of soft iron be raised while it is subjected to 
a weak magnetization force the first effect is to increase 
the magnetization. After passing a temperature of about 
1,200 degrees F. the increase is very rapid and may be 
ten- or twentyfold. Then, upon approaching a critical 
temperature, which differs with the specimen under con- 
sideration, (varying all the way from 770 to 800 degrees 
C.) the magnetism falls very rapidly and the whole of it is 
lost while the temperature is further rising ten or twelve 
degrees. Under moderate magnetizing force very little 
increase of magnetism is caused by a rise of temperature 
and under powerful forces no increase occurs. But in all 
cases the magnetism entirely disappears at the critical 
temperature. In general, the harder the specimen the 
lower is its critical temperature. 

TWO KINDS OF MAGNETISM. 

There actually are two kinds of magnetism. First there 
is the kind which has just been described — and which may 
very readily be called "red and blue" magnetism, re- 
ferring to the red and blue poles and the application of 
the laws of attraction and repulsion. Then there is the 
phenomenon which is known as Magnetic Induction. If 
you suspend a horseshoe magnet from a height and fasten 
a wire nail to a peg by a string just long enough so that 
the nail, if held up straight toward the magnet just misses 
touching it, then the wire nail will be drawn toward the 
magnet by what is known as induction. It is thus held 



112 EADIOTELEPHONY 

suspended in the air, being attracted toward the magnet 
but never quite touching it by reason of its retention at 
the end of the string. Thus we have a magnet magnetiz- 
ing another piece of metal without being in actual contact 
with it. 

You can easily make a magnet for yourself. Take a 
knitting needle or long sewing needle, or if desired a long 
steel bar. Mark the end which you desire to become the 
north pole with a file mark or scratch. Then lay the 
needle down on the table. Take a magnet and place its 
north pole on the end of the needle which you marked A, 
to become the north pole of the new magnet. Pressing 
gently on your magnet draw it several times from A to 
the opposite end, always in the same direction. Then 
take the south pole of your magnet and place it on the B 
end of your needle (opposite from A). Be sure that you 
carry the magnet from one extreme end of the needle to 
the other at each stroke and always see to it that north 
pole of the magnet is contacted with the north pole of the 
needle and vice versa. 

NORTH AND SOUTH POLES. 

Another way to make a magnet is to place the needle 
on the magnet, the desired north pole of the needle co- 
inciding with the north pole of the magnet and vice versa. 
Then hammer on the needle or bar repeatedly with a 
wooden mallet. The same result may be obtained by 
selecting a bar just long enough to bridge across to both 
poles of an electromagnet. The bar is tapped as was the 
case before. 

If a magnetized knitting needle be broken at its middle 
point each half of the needle is found to be a magnet. 
The ends which were north and south poles before break- 
ing remain north and south, while the broken ends become 




3^ 

g.0) 



o 

31 



5 s 



Pi 



o £ 

o r 

£§ 



O o£ 



N 0) 






O 

c£ v ■ 

si d 

t_ <t-l +-> 

S m rt 



N O 



MIRACLE OF THE AGE 113 

north and south poles alternately. The half needles may 
be broken again into equal or unequal portions and this 
process continued, the result being the same each time. 
The poles of every short piece of the needle appear 
weaker than the original poles. This is due chiefly be- 
cause the poles are so much nearer together and the re- 
pulsion of one pole nearly equals the attraction of the 
other pole and therefore it nearly counteracts. Hence, 
you may think of a magnet as being built up of an im- 
mense number of particles, each having a north and a 
south pole. In the body of the magnet the north pole of 
one particle being so closely in juxtaposition with the 
south pole of the next particle the effect is neutralized. 
But the unneutralized poles at the ends of the magnet 
form the true poles. 

There is such a thing as reaching the " saturation 
point' ' of magnetism. This is nothing more nor less than 
the point beyond which it is impossible to produce further 
magnetization in a given body. It is a recognized theory 
that in iron or steel the individual molecules are minute 
magnets, each with a north pole and a south pole. If the 
iron be unmagnetized the molecules are arranged at ran- 
dom so that, there being on the average equal numbers 
of molecules facing in all directions, the iron as a whole 
does not behave as a magnet. When the iron is subjected 
to a magnetizing force the molecules are twisted around 
more or less so that a large number face in the same or 
nearly the same direction. The iron then behaves as a 
magnet. When all the particles are set exactly in the 
proper direction it is impossible to magnetize the iron 
more strongly, which has been discovered by Joule to be 
the case (the same Joule from whom was named the unit 
of electrical measurement). When powerful electro- 
magnets are employed to magnetize a body a limit to the 



114 EADIOTELEPHONY 

magnetization soon is reached. Here we have the satura- 
tion point. 

VARIATION OF THE COMPASS. 

The direction in which a magnet points varies with the 
true north and south in different parts of the world. If 
undisturbed by magnets or iron bars near to it, the red 
pole of a magnet actually points to what is known as the 
magnetic north and the vertical place passing through 
magnetic north is called the place of the magnetic merid- 
ian, just as the plane passing through the true north is 
called the plane of the true meridian. The angle of vari- 
ation between the true meridian and the magnetic merid- 
ian is called the magnet declination and mariners call 
it the variation of the compass. Magnetic dip is the in- 
clination of the red pole (in the northern hemisphere) 
and the blue pole in the southern hemisphere toward the 
earth's surface. In England this magnetic dip amounts 
to as much as seventy degrees. At the equator there is 
no dip. This is known as the magnetic equator. 

Since the earth behaves like an enormous magnet all 
bodies of iron or steel whiclj are near to it are magnetized 
by induction. You know what happens to a magnet if it 
be hammered. The induction is greater. Thus, hammer 
heads and pokers are almost invariably found to be mag- 
netized. They are not, as a rule, powerful enough to pick 
up filings but their poles are very decided and they can be 
detected very easily by their action on a pocket compass. 
In the northern hemisphere, in which of course these 
United States of ours are located, a vertical column or 
strut or steel mast will have a red pole at its lower end 
and a blue pole at its upper end. 

The unit of measurement in determining strength of 
magnetism is the unit pole. A unit pole is one such that 
when placed at a distance one centimeter from another 



MIRACLE OF THE AGE 115 

unit pole it exerts a force of one dyne. The force exerted 
by one pole upon another is of course affected by the dis- 
tance. Accurately this relationship varies inversely as 
the square of the distance, between the poles. 

MAGNETIC FIELD. 

A magnetic field is that space which surrounds a mag- 
net. It can be seen that the area about a magnet differs 
from that which surrounds a space where no magnet is 
present. In the one a force acts upon any small magnet 
or piece of iron which may happen to be present, and in 
the other no force acts. Anywhere near the earth there 
is bound to exist a magnetic field which is due to the 
earth's magnetism but which is very weak as compared 
with the field of a common steel magnet. 

You can very easily trace the normal outlines of a mag- 
netic field for yourself by the following experiment. Take 
a magnet and place it upon a sheet of paper. Sift some 
fine iron filings through a piece of gauze so that they are 
sprinkled evenly over the paper, tap the paper gently and 
you will find that the filings arrange themselves in a series 
of curved lines from pole to pole and the space above the 
magnet itself is left almost free from filings. The in- 
tensity of a magnetic field at any given point is measured 
by the force which would act on a unit pole if placed at 
that point. As a rule the intensity changes as we go from 
one point to another. At any point near to a magnet there 
is a magnetic force acting in some direction or other. 
Hence, the whole space surrounding a magnet is densely 
packed with an infinite number of lines of force. At some 
points these lines are packed together more densely than 
at others. Where they are crowded, as near the poles of 
a magnet, the magnetic force is great. Wherever the lines 
are sparse the force is slight. 



116 EADIOTELEPHONY 

These lines of force and the principles of magnetism 
which have been drawn in this chapter play a large part 
in connection with electricity, directly, and radio indi- 
rectly. The fundamentals of electricity will be dealt with 
in the next chapter. 






CHAPTER XII. 

What Is Electricity — The Amber Kod — Glass Rod — 

Sealing-Wax Rod — Vitreous and Resinous Electricity 

— Laws of Attraction and Repulsion — The Proof Plane 

— The Electroscope. 

WHAT has made Eadio, the Marvel of the Ages, 
possible! Electricity. And what, after all, is 
electricity? Electricity goes very far back into 
history for its discovery and yet those who first discovered 
it did not realize what it was they had come into contact 
with. The Greek word for amber when translated into 
English spells electron, a word which modern scientists 
have usurped and applied to a certain unit of measure- 
ment of electricity. Amber it was that first made plain 
the fact that there was in existence a certain subtle force 
which exerted peculiar effects under certain conditions. 
For instance, generations and generations ago it was com- 
mon knowledge that a piece of amber when rubbed would 
attract straw, dry leaves, and other light bodies. History 
proves that this fact was mentioned as early as 600 B. C, 
the authority being Thales of Miletus. Other "Bef ore- 
Christ" works which have mentioned this phenomenon 
are Theophrastus (B. C. 321) and Pliny (70 A. D.). Then 
there came a wide gap and no great further experimenta- 
tion seems to have been done until along about the six- 
teenth century, when the celebrated Dr. Gilbert of Col- 
chester found that almost all bodies when rubbed behave 
in a similar manner. 

A glass rod rubbed vigorously with a silk handker- 
chief, or a stick of sealing-wax rubbed with flannel or 
catskin or chamois will, if held two or three inches above 

117 



118 EADIOTELEPHONY 

a little heap of pounded glass or snips of paper or bran 
meal or any other small and light pieces of matter attract 
them vigorously. But immediately upon touching the 
rod they are as vigorously repelled, scattering the heap in 
all directions. It is true that one or two small scraps of 
the paper or whatever is used may get flat on the rod and 
cling to it for a minute or two before being repelled. 
Small pieces of gold leaf may be lifted five or six inches 
and they will dance up and down between the rod and the 
table. 

ELECTRICITY NOT PRODUCED, BUT LED. 

The attraction of the glass rod and the sealing wax 
after they have been rubbed is due to nothing else than 
their electrification. The attraction is caused by the elec- 
tricity produced in the rubbed object. Here, however, is 
a point that it is well to bear in mind. "Produce" as 
used here does not imply the literal sense of the word. 
Electricity is not actually produced but it is rather "led 
forward," not being created but merely adapted to the 
existing condition, caused by the friction. Heat will flow 
from a hot body to a colder one and yet heat is not a fluid. 
In many cases you even yet hear the expression "elec- 
trical fluid." That is incorrect because electricity, al- 
though it undoubtedly does flow, is not a fluid. In fact, it 
is not a substance of any sort. There is no "stuff" in it 
as there is in air or in water. Your experiments with the 
rubbed glass and sealing-wax rods proved to you, if car- 
ried on a bit further, that there are two kinds of electric- 
ity — vitreous or positive and resinous or negative. The 
electricity generated in the glass rod is of the vitreous or 
positive type and that generated in the sealing-wax rod is 
of the resinous or negative type. 

Bodies which readily allow electricity to flow through 



MIRACLE OF THE AGE 119 

them are called conductors and bodies which prevent its 
flow are called nonconductors or insulators. A body 
which has been electrified must be insulated or cut off 
from other bodies which might take away their "charge." 
This is done by means of glass supports or ebonite sup- 
ports, or by means of suspension with silken thread. 
Bodies thus suspended in the air, free from physical con- 
tact with other bodies which would rob them, retain their 
electricity. Thus it is shown that the air is a good insula- 
tor. It is found that all dry gases at the ordinary atmos- 
pheric pressure are good insulators. 

THE ELECTROSCOPE. 

The electroscope is a delicate little instrument designed 
to detect and designate feeble changes of electricity, as to 
their nature. The same thing may be accomplished by 
means of what is known as a proof plane. This is simply 
a small piece of tinfoil (or almost any other metal) at- 
tached to a glass or ebonite handle. If an electrified body 
be touched with the proof plane a specimen of the elec- 
tricity of that body is taken away by the proof plane, 
which in turn becomes charged. Suppose, then, you sus- 
pend a small pith ball, which has been charged positively, 
from a silken string. If the proof plane be presented to 
this ball the latter will be found to be attracted or repelled 
according to whether the plane is charged positively or 
negatively. 

If you take a rod which has been charged with positive 
electricity and bring it near to an uncharged insulated 
metallic body, you will find by means of the proof plane 
that the end of the body nearest to the rod becomes 
charged with negative electricity and the part furthest 
from the rod charged with positive electricity, the middle 
parts being neutral. These charges of electricity are said, 



120 EADIOTELEPHONY 

as in magnetism, to be induced and the phenomenon is 
called induction. 

The law of magnetism whereby like bodies repel and 
unlike bodies attract likewise holds good in electricity. 
But where does electricity come from? It is intangible. 
You cannot reach out and touch it. You cannot wrap it 
up in a paper parcel and sell it over the counter like a 
pound of sugar; but as modern science makes one step 
after another along the line of electrical development this 
intangible aspect is more and more overcome. For the 
present let us think of all unelectrified bodies as contain- 
ing an unlimited supply of positive and an equally un- 
limited supply of negative electricity (whatever those two 
quantities may be). The attractions and repulsions of 
these two neutralize each other. A body which has an 
excess of positive electricity (or a deficit of negative elec- 
tricity) is said to be positively electrified and vice versa. 

TWO KINDS OF ELECTRICITY. 

It may be a difficult thing to imagine a single body as 
being possessed of two different kinds of electricity, each 
exactly opposed in nature to the other kind. Franklin's 
suggestion was that there is but one kind of electricity, 
that all unelectrified bodies contain a certain normal 
amount of this electricity and that positively charged 
bodies are those with more than the normal amount. This 
still leaves to be considered the difficulty that the normal 
amount of electricity in a body must be practically un- 
limited, for to produce a very intense negative charge a 
very great amount of electricity would have to be with- 
drawn from any given body. 

Here you have three simple rules which may help you 
to visualize the general theory of electricity. An unelec- 
trified body with its equal amounts of positive and nega- 



MIKACLE OF THE AGE 121 

tive electricity may be charged positively in three ways : 
— first, by being given more electricity ; second, by taking 
electricity away; and third, by both giving and taking 
electricity away simultaneously. 

On the other hand, a positively electrified body may 
have its charge weakened in three ways : — first, by taking 
away positive electricity; second, by giving it negative 
electricity and, third, by taking away the positive and 
giving it the negative electricity simultaneously. Any 
one of these ways, if pursued far enough, will equalize the 
amounts of positive and negative electricity in the body 
and then give it an excess of negative electricity. 

ALL PAIRS OF BODIES ELECTRIFIED. 

The gold-leaf electroscope is an extremely delicate little 
instrument used to detect the existence of feeble charges 
of electricity. The electroscope is arranged with two 
leaves of gold forming the terminal of a brass wire which 
leads from a brass contact plate. If this brass contact 
plate is touched with a body charged positively, negative 
electricity is driven into the plate and positive electricity 
is repelled through the wire into the gold leaves. The 
leaves, being similarly electrified, repel one another and 
open out. Thus, since you know whether it is negative or 
positive electricity that produces the divergence of the 
gold leaves, the instrument may be used to detect the na- 
ture of any charge of electricity, even the most feeble. 

The gold-leaf electroscope has proved conclusively that 
all pairs of bodies are electrified when rubbed together, 
one becoming charged negatively and the other positively. 
In the case of metals and other conducting bodies this 
might appear to be untrue. The reason is that any elec- 
tricity which is produced upon them immediately escapes 
to the earth if the conductor be handled during an experi- 



122 EADIOTELEPHONY 

ment in the same way as we handle the sealing-wax rod 
or the glass rod, etc. If, on the other hand, a brass rod 
be stuck into an insulating glass handle the rod, on being 
rubbed or flipped briskly with dry silk, becomes electri- 
fied. Sometimes this experiment fails, due to the fact 
that the handle insulation is not altogether perfect. A 
sure way of illustrating the fact that brass actually can be 
electrified is to uncharge an electroscope and then flip 
with a piece of silk the brass plate of the electroscope. If 
the electroscope be perfectly dry before you start the ex- 
periment it will be necessary to make but a very few 
strokes of the silk before you notice wide divergence of 
the leaves. In several places the substance ebonite has 
been mentioned. This is a combination of sulphur and 
India rubber. 

The wonders of electricity never cease and as you go 
more and more deeply into the subject you cannot help 
but marvel at the seeming miracles that may be per- 
formed with it. For instance, you have seen how there is 
a very definite distinction between negative and positive 
electricity. And yet you will now see how it is possible to 
charge a body negatively and then take from that body a 
positive charge. This is accomplished by means of what 
is known as the electrophorus. 

THE ELECTROPHORUS. 

The electrophorus is an instrument consisting of a thin 
cake (about one-eighth of an inch thick) of some resinous 
material, such as shellac, sealing wax, etc. This thin cake 
is cast in a shallow metal dish or sole. On the resinous 
cake there lies a disc of brass, or any other metal, which 
is known as the cover. This cover is furnished with an 
insulating glass or ebonite handle and is slightly smaller 
in diameter than the sole. 



MIRACLE OF THE AGE 123 

In many cases a small knob is fixed by a short stem on 
the top of the cover. The cake is electrified negatively by 
rubbing with flannel or striking briskly with catskin. The 
cover now is placed on the sealing-wax cake and since 
neither of them can be absolutely flat they come into con- 
tact only at a limited number of points, the greater part 
of their surfaces being separated by a minute air gap. 
At the few points where contact is maintained the sealing 
wax gives up its negative electricity to the cover but the 
negative electricity distributed over the rest of the sur- 
face is unaffected, being unable to escape along the 
nonconducting sealing wax. The cover is affected by in- 
duction, from the negative electricity, and it becomes 
electrified, positive electricity being attracted to its 
lower surface and negative electricity driven to its upper 
surface. Now, if you touch the cover with your finger the 
negative electricity will escape through your body to the 
earth. This is the principle of "grounding" which plays 
such a large part in all electrical construction work. 
Finally, if you lift the cover by the insulating handle, 
being careful to take hold at the extreme end, the positive 
electricity, being no longer attracted to the under surface, 
is free to distribute itself over both surfaces and the 
cover is found to be charged with positive electricity 
throughout. If you now present it to the electroscope you 
will find that it causes a very decided reaction from the 
instrument. 

STRANGE FACTS ABOUT ELECTRICITY. 

If the knuckle of the hand be presented to the knob, the 
charge escapes from it to the hand just before actual con- 
tact takes place. In other words, the spark " jumps.' ' 
As a result, a slight tingling prick is felt, a faint but de- 



124 EADIOTELEPHONY 

cided crack is heard and the spark itself actually may be 
seen. 

At this point it might be well to emphasize the fact that 
a charge of electricity rests entirely upon the surface of 
a charged body and does not penetrate it beyond the sur- 
face. Definite and interesting experiments proving this 
conclusively to be true have been worked out but they are 
more or less complicated. Suffice it to say that it has been 
proved that a charge of electricity does not penetrate a 
body more than one one-hundredth of an inch below the 
surface. 

If you have ever talked to anyone who worked in a 
paper mill you will know that this principle does work out 
in practice. The newly-made paper, being damp, is 
passed between several heated rollers to dry it, which 
process electrifies it feebly. But as the continuous strip 
is wound around and around into an immense roll and the 
electricity of each turn passes to the outside as soon as it 
is covered by another fold, the surface of the roll soon 
becomes powerfully electrified by the accumulated 
charges. If the knuckle now is presented to the paper a 
brilliant spark is the result and often a more than severe 
shock is produced. 

ELECTRO SURFACE DENSITY. 

Naturally, since electricity is seen to confine itself to 
the surface of a body, you would expect that it would 
spread itself out evenly in all directions. In bodies of 
symmetrical shape this is true. But in bodies which have 
protuberances, the electricity is accumulated on the more 
prominent parts of the surface and almost absent from 
any depressed parts. Electro surface density is a term 
used to express the intensity of accumulation of electric- 
ity at any part of the surface. The surface density is 



MIRACLE OF THE AGE 125 

greatest at all points, edges or corners. Electro surface 
density at any point is the number of units of electricity 
per square centimeter at the point. 

You know that electricity leaves the interior of a con- 
ductor and distributes itself on the surface. The same 
repulsion makes it endeavor to disperse more widely still. 
This is prevented by the fact that the surrounding air is 
a nonconductor. However, the tendency on the part of 
the electricity toward further dispersion puts the sur- 
rounding air under what is called "electrical tension." 
Whenever the surface density is sufficiently increased 
(which may be done either by giving a very strong charge 
to a conductor of moderate curvature or a moderate 
charge to a conductor with points or parts sharply 
curved) the tension becomes too great for the air to with- 
stand and it gives away with a disruptive discharge, the 
discharge being accompanied by a smart crack and a visi- 
ble spark. Here, then, is at least one instance where we 
can see electricity. 

HEARING ELECTRICITY. 

From a sharp point on a charged conductor electricity 
will escape continuously with a hissing sound and in a 
dark room a faint glow is visible around the point. If 
there be no other conductor near the point to which the 
electricity can escape it will charge even the air itself 
near the point. The charged air then is repelled from the 
point and, streaming away, it forms a wind. This may 
be proved by holding a lighted candle before the discharg- 
ing point of an electrical spark machine. Hence, you can 
see at a glance that any conductor intended to retain a 
charge for a considerable length of time should be free 
from sharp angles or points. 

In the next chapter will be discussed the various 



126 EADIOTELEPHONY 

types of electrical machines, showing just how electricity 
is produced and the various elements which enter into its 
handling 1 . Also, it will be shown just how the elementary 
principles of electricity are developed and applied spec- 
ifically and practically to radio, making the radio the 
most wonderful development or invention of many gener- 
ations. 



CHAPTER XIII. 

Electrical Machines — Newton, Hawksbee, Ramsden, 
Yon Guericke — Wimshurst Machine — Leyden Jar — 
Strain In the Air — Can Electricity Pass Through 

Glass? 

ELECTRICITY, although it is a most intangible 
force, is at the same time a force with which man so 
far has been able to do more than perhaps with any 
other. And, though it is apparently so very intangible, 
man has harnessed it and regulated it and actually pro- 
duced it — we might say, artificially. If we lay aside the 
scientific data and proof which modern scientists have 
given ns and permit our minds to rest on electricity in the 
abstract we cannot help but think of the very intangible, 
elusive ' ' substance ' ' which Franklin and his kite tied up 
with civilization. And yet electricity is a very definitely 
tangible thing and its control is a very positive proposi- 
tion. It might be of more than passing interest to delve 
for a short space into the ways of producing electricity 
by means of so-called "machines." 

The earliest machine was invented about 1640 by Otto 
von Guericke, who was also the inventor of the air pump. 
His machine consisted of a ball of sulphur of rather large 
proportions mounted on an axle. This ball of sulphur 
was rotated and while one man turned the axle another 
man held his hands against the sulphur. The friction 
thus produced brought forth electricity, which was led 
away to a "conductor" by means of a chain hanging 
against the ball. 

Various other experiments were conducted by Newton, 
Hawksbee, Ramsden, Winter and others. Newton, for in- 

127 



128 EADIOTELEPHONY 

stance, used a glass globe instead of the ball of sulphur. 
This was the origin of the frictional machine. Develop- 
ment has led to the supplanting of the frictional machine 
by the induction machine, in which only a slight amount 
of friction is necessary to produce an initial charge and 
the subsequent supply is obtained by induction, as is the 
case in the electrophorus. 

PLATE ELECTRICAL MACHINE. 

You undoubtedly have heard of the plate electrical ma- 
chine. This consists of a circular plate about 20 inches in 
diameter which is mounted firmly on an axis and can be 
turned by a handle. At the top and bottom of the plate 
are pairs of cushioned rubbers through which the plate 
passes. These rubbers are made of silk or leather tacked 
on to wooden blocks and stuffed with horsehair. They 
are so arranged that they can be adjusted to vary the 
pressure on the glass. Then, we have a pair of combs, 
formed by brass rods which are bent around the edge of 
the plate and fitted with a number of points or needles 
directed toward the plate. 

The plate in being rotated between the rubbers develops 
positive electricity. As the parts charged with the posi- 
tive electricity pass between the combs they act induc- 
tively, repelling positive electricity into the remote parts 
and attracting negative electricity into the points. You 
know that electricity is repelled from points, hence this 
negative electricity is thrown off from the points of the 
combs to the plate and there it neutralizes the positive 
electricity under the points themselves. The continued 
rotation of the plate brings fresh supplies of positive elec- 
tricity to be neutralized by the withdrawal of more and 
more negative electricity from the combs ; the conductor, 
having a greater and greater deficiency of negative elec- 




Copyright, Underwood & Underwood, N. Y. 
HENRY FORD PUTS ON THE RADIO PHONE RECEIVERS 
Henry Ford dropped into an Atlanta (Ga.) newspaper office and 
listened in on the radio phone receiving set installed by the newspaper. 




Copyright, Underwood & Underwood, N. Y. 
GOOD MORNING GREETING 
This young lady is seen at the window of her room in the McAlpin 
Hotel, New York, as she gets a greeting from a young man in Brookline, 
Mass. She is able to send and receive messages. 







C,bo 



ci a) . 
w — 

>> v. 

X3 "-i at 
§--« 
o+->— • 

£ £2 'I 

E-i "^ <p 



v: 



2 G 2^ 
< o * 

rt.S be 

5a§ E 

« ST* 
£ |.2« 

M "3 to 
J .c-r bo 

* g So « 

O J S 09 c 

W O 



^ o 
3 u 
-a 



'She- 



C aJ"E 
How 




2* v 
En 3+J 

I" 5 

TO (D 
G bO 

iSo.S 



oo"£ 

§11 

H _ ** 
ICQ 



G c3M 



°1* 

-G bo 
-G >> . 

°g£.5 

sgag 



U (O <v 



C . d 

MO, .S3 2 

SSI'S 



G 


2 « o> o 


O 


a 

G 


■* 3d 


does 

adio 

pict 

bro 






^01*' 




<u -1 


G 


mor 

-day 

as 

once 


hn 


+J 0J o 




° G G 


>» 




a 


0) wo 


o 


^ d 


U 


ad t- 



MIEACLE OF THE AGE 129 

tricity, is charged more and more powerfully with posi- 
tive electricity. 

Still another form of electric machine is derived from 
the principle of " electric wind," which was explained in 
a preceding chapter. This machine consists of five or six 
brass wires radiating from a central cap which can be 
balanced on the top of a pivot. The wires have their ends 
sharply pointed and bent to point in the same way around 
a circle. When the pivot is connected with the electrical 
machine electricity makes its way to the points of the 
wires and there escapes into the air. The electrified air 
is repelled from the points but by reason of Newton's 
third law there must be an equal reaction on the points. 
Therefore they are driven backwards and so long as the 
machine is working well the wheels spin rapidly. A still 
further experiment with this machine was effected by 
inverting over it a bell jar. After a few minutes the air 
in the jar became so highly electrified that further escape 
of electricity from the machine was prevented and the 
machine came to rest. 

THE WIMSHURST MACHINE. 

The Wimshurst Electrical Machine is the simplest and 
most perfect of the machines worked by induction. It 
consists of two circular glass plates, about 20 inches in 
diameter in a medium-sized machine, mounted on a sub- 
stantial frame. The plates are geared so that they rotate 
in opposite directions, with the smallest possible clear- 
ance between the plates. On the outer face of each plate 
there are stuck an even number of strips of brass or tin- 
foil. The spaces between these strips, as is also the case 
with the rest of the surface of the plates, are varnished 
well to prevent electricity from leaking over the surface. 
At each end of the horizontal diameter of the plates is 



130 EADIOTELEPHONY 

placed a conductor with branches upon which there are 
placed combs or rows of points directed toward the plates. 
These conductors are supported by glass or ebonite 
handles. These conductors terminate in discharging rods 
which have knobs at their ends. These discharging rods 
can be adjusted, even while the machine is in operation. 
A conducting rod with a small brush of very thin brass is 
placed so that it contacts with the front plate; and a 
similar brush touches the back plate. 

In practical use, there is always a sufficient charge of 
electricity present in the machine, left over from the pre- 
ceding use, to work up a powerful electrification from a 
few turns of the plates. However, if there be absolutely 
no electrification left it is a simple matter to touch against 
the back of the plate an electrified ebonite rod. 

If the machine be worked in the dark a beautiful glow 
is seen on the plates. This glow is caused by the electrical 
leakage over the plates. From all of the little points 
delicate brushes of violet light may be seen. These violet 
brushes are due to the streaming of electricity from the 
points themselves. A series of brilliant sparks will be 
forced across the gap between the adjustable knobs, even 
when those knobs are as far apart as four or five inches. 

DISCOVERY OF LEYDEN JAR. 

The Leyden jar was discovered in 1746. Cuneus, a 
student at Leyden, in Holland, seeking to electrify water, 
took in his hand a glass flask half filled with water and let 
dip into the water the end of a chain hanging from the 
conductor of a "glass-globe machine." Some time hav- 
ing been allowed to get the water well charged he at- 
tempted to lift the chain from the flask and received a 
violent shock in the arms and chest which caused him to 
drop the flask. It took him two days to recover from the 



MIRACLE OF THE AGE 131 

effects of his experience. This discovery caused great 
excitement in the scientific world, it being the first electric 
shock ever experienced, with the exception of theretofore 
unrecognized lightning strokes. Improvements were 
made soon and the result was the discovery of the Leyden 
jar. 

The Leyden jar is a thin glass jar coated about half- 
way up both inside and outside with tinfoil. These tin- 
foil coatings act as plates or conductors. The Leyden 
jar originally was given the appropriate name "Accumu- 
lator ' ' but this name unfortunately has fallen into disuse, 
owing to its having been misapplied to secondary bat- 
teries. The name "Condenser" is more properly used 
but care must be taken to distingush here between the 
condensation which takes place with steam and that which 
takes place with electricity. 

PREVENTION OF SERIOUS SHOCK. 

On the inner coating of the Leyden jar there is a brass 
rod which is terminated by a knob. In some of the more 
usual forms this rod is passed through a wooden lip or 
cap and from its lower end hangs a piece of chain which 
makes contact with the inner coating. The cap keeps out 
the dust but it does admittedly furnish in itself a possible 
leak which is obviated in the form which has no cap. 
There insulation is pretty nearly perfect because leaking 
electricity would have to pass up the surface of the glass 
on the inside and down the outer surface. The Leyden 
jar is provided with a discharger which prevents serious 
shocks. This discharger consists of a pair of brass rods, 
fitted with knobs at one end, jointed together at the other 
and mounted on a glass handle. One knob placed in con- 
tact with the outer coating and the other up to the knob 
of the jar, discharges the jar. 



132 EADIOTELEPHONY 

We have described the shock experienced by a single 
individual. The same shock may be felt simultaneously 
by any number of people provided they join hands so as 
to make a continuous chain. The man at one end must 
hold the jar by its outer coating while the man at the other 
end touches the knob. In some French experiments made 
during the excitement which followed the discovery of the 
Leyden jar a severe shock was thus given to a whole regi- 
ment of about 1,500 soldiers. 

SHOCKS FELT AND NOT FELT. 

Shocks also may be given from Voltaic Batteries, 
Buhmkorff Induction Coils and Dynamos. No shock 
whatever is felt when we touch the terminals or wires con- 
nected with the terminals of a battery containing two or 
three cells. If the number of cells be increased to ten a 
slight pricking sensation is felt when a wire from a termi- 
nal is held very lightly in the hand. The effect is more 
evident if the hands have previously been soaked in water 
to which a trace of acid has been added. It is then accom- 
panied by a slight twitching of the muscles. These sensa- 
tions become much more marked as the number of cells is 
increased to 40 or 50 and are felt to a similar extent with 
a low pressure dynamo — one giving a difference of po- 
tential of 50 to 100 volts. A nasty shock is given by 100 
to 150 cells or 200 to 300 volts and anything above this is 
distinctly dangerous. A shock from a dynamo working 
at 600 to 1,000 volts is as a rule fatal even if given by a 
momentary accidental contact with a wire. The danger 
arising from the enormous potentials (ten to twenty thou- 
sand volts) often employed in electric lighting stations 
is very great and the utmost caution has to be observed in 
their use. 

If the knobs of the Wimshurst machine be separated by 



MIRACLE OF THE AGE 133 

a short distance (half an inch or less) the spark usually 
consists of only a single bright line of light which on ex- 
amination shows at the negative knob a very brilliant 
point separated by a stretch of purplish violet light from 
a longer brilliant line which extends to the positive knob. 
If the distance be increased to two or three inches or more 
the discharge breaks up into a number of sparks similar 
to the last, side by side and slightly bowed outward, as 
though they repelled one another. 

The spark from the Leyden jar is much brighter, 
stouter and gives a sharper sound than the direct spark 
between the knobs of the machine. This is due, of course, 
to the greater quantity of electricity which passes. If 
the conductors of a Wimshurst machine be connected 
with the inner coats of two Leyden jars the outer coats 
of which are connected together, then a spark only passes 
between the knobs when each jar is fully charged. It, 
therefore, has all the characteristics of a Leyden jar 
spark. 

STRAIN BY ELECTRICITY. 

You have seen that the jar around an electrified body 
is strained by the electricity and when the strain at any 
point becomes too great a passage for the electricity is 
torn through the air and the whole charge rushes through. 
The sound of the spark probably is due to the tearing 
asunder and subsequent closing in of the air. Heat is 
produced by the friction of this sudden rush of air and 
therefore the spark is able to ignite charges of gunpowder 
or spirits and to produce an explosion in a mixture of 
oxygen and hydrogen. 

It may seem strange that any " strain' ' can exist in so 
mobile a substance as the air but it must be remembered 
that although ordinary matter passes readily through the 



134 EADIOTELEPHONY 

air and therefore cannot cause strain on it the passage 
of electricity is opposed in air just as much as the passage 
of ordinary matter through some such substance as glass. 
Electricity causes strain in other insulating materials and 
the strain amounts to an actual rupture or piercing, in 
any case where a spark passes through the material. The 
spark from a Wimshurst machine will puncture a card 
placed between the knobs of the machine. The hole thus 
made has a slight burr on each side as though it were 
burst outward from the middle. A sheet of glass may be 
pierced by the spark but unless it be very thin a powerful 
spark from a battery of Leyden jars is necessary. Here, 
however, it is necessary to take the greatest precautions 
to guard against the spark leaping around the glass in- 
stead of through it. 

HEATING EFFECTS OF ELECTRICITY. 

To demonstrate the heating effect of electricity a fine 
wire placed in the path of the electricity when a spark is 
taken from a battery of Leyden jars is heated and becomes 
red hot, white hot or even melts, according to its fineness. 
Gold leaf placed in the circuit is raised to a high tempera- 
ture owing to its extreme thinness and it is not merely 
melted but volatilized, or converted into vapor. It has 
been proved very conclusively and concisely by Coulomb, 
with the help of his torsion balance, which we will not 
describe here in detail, that like electricity repels and un- 
like electricity attracts. But he went further than that 
and established a law covering the force with which this 
attraction or repulsion takes place. This law is that "the 
force between two small electrified bodies varies inversely 
as the square of the distance between them." From 
Coulomb the unit of electrical measure, the Coulomb, was 
named. 



MIEACLE OF THE AGE 135 

The next chapter will discuss electricity as it is found 
in the air, touching upon the history of Franklin's experi- 
ment, and the developments that have followed that ex- 
periment. This, with a short study of electro-magnetism, 
brings us into the actual working conditions surrounding 
the practical application of these principles that have 
been discussed in the last four chapters, to the broad and 
ever interesting subject, Radio. 



CHAPTER XIV. 

Franklin and His Famous Experiment — What is Light- 
ning? — Effect of Atmospheric Change on Electrical 
Conditions — Electro-magnetism in Wires, Coils and 
Spirals — Effects of Thunderstorms — First Use of Wires 
for Telegraphic Transmission — The Wire Eliminated. 

JUST six years after Cuneus had his painful and star- 
tling experience with the Leyden jar, whereby he was 
severely shocked and the scientific world of that day 
was awakened to the potentialities of electricity, there 
came the experiments of the great Benjamin Franklin 
(1752) which are pretty well known because of their con- 
stant preachments in the public schools of the country. 
The similarity of the jagged lightning flash and the smart 
spark obtained from the f rictional machine and the Ley- 
den jar suggested to Franklin, among others, that light- 
ning was nothing more nor less than a gigantic spark 
leaping about in the heavens from one cloud to another or 
from a cloud to the earth. Franklin and his contemporary 
experimenters were quick to perceive the similarity be- 
tween the lightning ' ' stroke ' ' and the shock of the Leyden 
jar. And these men recognized that a peal of thunder 
was but a magnification of the cracking of the spark £rom 
a machine. 

Franklin's original experiment consisted of flying a kite 
near the clouds during a storm and attempting to draw 
electricity down to him along the string. At the end of 
the string he hung a key, from which to draw the sparks 
if any came. He held the string by means of a silk ribbon 
in order to insulate it. At first the string was dry and no 

136 



MIEACLE OF THE AGE 137 

result was obtained but as soon as rain fell the string be- 
came wetted and conducted an abundant supply of elec- 
tricity to the key, which then yielded powerful sparks. 
This type of experiment was extremely dangerous be- 
cause on occasions sparks as long as nine feet were 
produced. In 1753 Eichmann, a Eussian physical experi- 
menter, was killed by a shock. 

Having established the general truth that clouds gen- 
erally are electrified we are confronted with the problem 
of "how do they become electrified " — in some cases to 
such an enormous potential that they can yield sparks 
possibly a mile long? The problem is one upon which 
eminent scientists have been working more or less unsuc- 
cessfully until now. Doubtless the electrification is due 
largely to friction of the wind against the surface of the 
earth while another agent may be the evaporation of 
water from the sea, from rivers and from moist land, 
which evaporation is taking place continually. 

HOT WEATHER AFFECTS RADIO. 

Wireless telephony, or as it is destined to be known 
more popularly — radio, seems to be largely affected dur- 
ing hot weather. The condition of the atmosphere has a 
great effect upon the daily results that can be obtained 
with it. Hence, the following brief discussion of the ac- 
tion of dry air as related to electricity will undoubtedly 
be of interest at this point. 

Dry air is one of the best known insulators. Hence, 
during a very dry spell there is little or no opportunity 
for electricity to escape from the air to the earth. There- 
fore, we logically might expect that the upper strata of 
the atmosphere would gradually accumulate the electric- 
ity which is continually being produced by friction and by 
evaporation. Eemember, however, that the air may feel 



138 BADIOTELEPHONY 

dry because it is hot and capable of holding a great 
amount of water vapor and yet it is continually drinking 
up more moisture, a process to which sooner or later an 
end must come when the air becomes nearly saturated. 
Ultimately some slight fall of temperature causes these 
upper strata to become moist, the water vapor within 
them begins to condense into minute particles, and clouds 
are formed whose conductivity may be fairly good. 
The electricity which, before the condensation, was dis- 
tributed throughout the volume of the air makes its way 
to the surface of the cloud and being thus packed more 
densely together it has a greater tendency to escape in 
sparks. 

Previous to a thunderstorm the clouds are in great com- 
motion, great masses being torn asunder, others uniting 
together. Now these clouds become electrified, some more 
or less strongly, and they act inductively on one another 
and if a piece happens to be torn away while more than its 
fair share of electricity has been induced into it, it may 
soar away intensely electrified. Several such pieces may 
unite to form a big cloud charged to the enormous poten- 
tial necessary to produce a flash of lightning. Neces- 
sarily, we can see at a glance what "interference' 4 with 
radio impulses will take place under conditions such as 
these. 

WHY BIG RAINDROPS FOLLOW THUNDER. 

You undoubtedly have noticed that just after a clap of 
thunder the drops of rain are very considerably larger. 
This is due to the fact that when drops of rain strike to- 
gether when slightly electrified they come together into 
big drops but that when they are unelectrified they gen- 
erally rebound on one another. Just before a thunder 
clap the drops are kept apart by the strong electrification 



MIEACLE OF THE AGE 139 

and just after the clap the feeble charge remaining causes 
them to coalesce into big drops. 

Franklin it was who first advocated and devised the 
lightning conductor. This consists, as you must well 
know, of stout copper conductors led down from the high- 
est possible point of the building to a " ground,' ' which 
may be effected by attaching to water pipes {never gas 
pipes) underground or by leading away into a damp spot 
and attaching to a metal plate, covered with coke. Why 
does a lightning conductor work? If a cloud strongly 
charged with positive electricity be floating above the 
building it induces negative electricity on the part of the 
earth immediately below and into the conductor itself. 
The negative electricity attracted into the points very 
readily escapes from them into the air and so long as the 
charged cloud remains overhead there will be a silent but 
potent stream of negative electricity flowing steadily into 
the air from the point of the conductor. Thus the elec- 
tricity of the cloud is gradually neutralized without the 
passage of a violent spark. 

DISCOVERY OF VOLTAIC CELL. 

During fine weather the air is almost always at a posi- 
tive potential. During wet weather it is sometimes posi- 
tive, sometimes negative. During snow it is almost 
always positive and if the wind be high the potential is 
about twenty-five times the fine weather potential. Dur- 
ing thunderstorms it may be positive or negative and 
sometimes as strong as fifty times the normal potential. 
Also the height affects the potential ; the higher we go the 
more the potential increases. 

In 1790 Galvani, a professor of anatomy at Bologna, 
observed curious convulsive movements in the muscles- of 
a recently-killed frog when touched at different points by 



140 BADIOTELEPHONY 

iron and copper which were in contact. These movements, 
resembling the muscular contractions experienced when a 
shock is taken from a Leyden jar, naturally suggested the 
thought that some electrical action was taking place. And 
the fact that Galvani observed similar action in the mus- 
cles of dead frogs when affected by ordinary electrical 
machines justified the assumption. 

Volta very soon thereafter proved by means of the 
" condensing' ' electroscope that certainly some electric 
action occurs when two different metals — for instance 
zinc and copper — are placed in contact. His experiments 
led to the discovery and application and improvement of 
the so-called voltaic cell. Currents thus produced have 
for many years been called Voltaic Electricity, Galvanic 
Electricity, but really there is no essential difference be- 
tween this and Frictional Electricity. 

You know that, if you are right-handed, the motion of 
driving a screw into a piece of wood with a screwdriver 
is a perfectly natural one. The screw being threaded in 
a right-hand direction there is but one course that your 
motion can follow and that is to the right. Now, imagine 
an electric current in the same fashion. Consider a wire 
carrying an electric current. This wire will be sur- 
rounded by circular lines of (magnetic) force and the 
direction of the current and of the lines of force are con- 
nected in the same way as the turning and driving in of 
the ordinary right-hand screw. This can be proved to 
your satisfaction by passing a powerful current, say ten 
amperes, along a stout wire which has been stuck at right 
angles through a sheet of paper — or, better yet, through 
a hole drilled in a sheet of glass. You will find that iron 
filings sprinkled on the sheet arrange themselves, when 
the sheet is tapped, in circles with the wire for their 
center. 



MIRACLE OF THE AGE 141 

Now, consider a wire bent into a loop. Here you will 
find that an electric current flowing around such a loop is 
equivalent to a flat magnetized disc of the same size as 
the loop, the north pole of the disc being on that face 
around which the current appears to flow anti-clockivise. 

ELECTRICAL EFFECTS IN SPIRALS. 

Now, if you bend the wire conveying the current into a 
spiral shape each turn of the spiral is practically such a 
loop as that just described and therefore is equivalent to 
a magnetized disc. The whole spiral is equivalent to a set 
of such discs all with their north poles facing to the left 
and the south poles facing to the right. The alternate 
north and south poles neutralize each other as far as 
external action is concerned and there remains an unneu- 
tralized north pole at one end and an unneutralized south 
pole at the other end. Such a spiral wire carrying a cur- 
rent is called a solenoid and it is equivalent to a mag- 
netized rod so far as concerns its action on bodies outside 
the spiral. The location of the north pole and the south 
pole is done not from the way of winding the spiral but by 
observing which way the current flows around. If the 
current be reversed the poles are reversed, although the 
spiral itself is unchanged. 

A circuit carrying a current tries to move so that as 
many lines of force as possible (due either to a magnet 
or to another current) pass through it in the same direc- 
tion as its own lines of force. Thus, electric current can 
make magnets and behave like magnets. Then the ques- 
tion naturally presents itself "Can magnets or currents 
behaving like magnets produce currents of electricity V 9 
Faraday's researches, conducted in 1831, answered the 
question in the affirmative and from the facts discovered 
by him the knowledge which renders possible the con- 



142 BADIOTELEPHONY 

struction of the gigantic dynamos of the present day has 
been gradually built up. 

As soon as it was discovered, more than a century ago, 
that electricity could be made to travel along a damp 
string or wire, which had been carefully suspended from 
insulating supports, the fluttering of the gold leaves of 
the electroscope and the movements of the pith balls at 
once suggested the idea of giving signals at a distance by 
means of electricity. 

THE FIRST ELECTRICAL MESSAGES. 

In 1747, at Shooters Hill, near London, Bishop Watson 
sent the shock from a Leyden jar through two miles of 
wire hung from wooden poles but this was a rather violent 
method of signalling. In 1774 Lesage, at Geneva, ar- 
ranged twenty-four long wires side by side and connected 
each to an electroscope at the far end. Each electroscope 
indicated a letter and therefore by charging the wires in 
proper order words could be spelled out. Owing to the 
uncertainty of all work with frictional electricity, espe- 
cially before the days of the Wimshurst machine, these 
attempts at telegraphy were of no practical use. 

The discovery of the voltaic battery put the matter on 
a different footing. In 1811 Sommering, of Munich, con- 
structed a workable telegraph but it was not until late in 
1837 that the telegraph was made capable of commercial 
use, as a result chiefly of the efforts of Steinheil, of 
Munich, Morse, of America, and Wheatstone and Cooke, 
of England. From Wheatstone comes the Wheatstone 
Bridge, a method of electrical measurement very largely 
experimented with by electrical students. 

As early as 1860 an instrument which bordered on the 
fundamental principle of telephony was designed by Eeis. 
This was capable of conveying musical sounds but it was 



MIEACLE OF THE AGE 143 

incapable of transmitting properly: the complicated 
sounds of the human voice. The receiver designed by 
Eeis was fairly perfect but the transmitter was the ineffi- 
cient part of the apparatus. The year 1876 brought from 
Alexander Grahamm Bell the instrument that became 
practically the parent of the modern telephone. The 
microphone transmitter, designed by Hughes in 1878, took 
the place of the Bell transmitter, although the original 
form of receiver continues to be the type of all receivers. 

Wireless telegraphy has been known in one form or an- 
other for a good many years. In 1859 Lindsay sent sig- 
nals across the Tay where it was three-quarters of a mile 
wide. In 1882 Sir W. Preece sent messages across the 
Solent from Portsmouth to the Isle of Wight. In 1886, 
when the cable to the Scilly Isles was broken down, mes- 
sages which were passing in the neighboring French At- 
lantic cable were readable on the broken-down Scilly 
cable. In 1892 Sir W. Preece sent a message a distance 
of three miles without wires. His signalling depended on 
electro-magnetic induction. 

Hertz (deceased in 1894), Branly, Prof. Oliver Lodge, 
Marconi — all played their part in the development of this 
most wonderful of all modern invention — the Radio. The 
history of their experimentations is too complicated to 
permit detailed discussion here but out of their experi- 
ments has come the greatest thing modern science has 
given humanity. 



CHAPTER XV. 

How We Hear Sounds — Sounds Exists Only Where 
There is Someone to Hear Them — The Telephone Trans- 
mitter and Eeceiver — In Radio Vibrations are Reduced 
to Bring Them Within the Scope of the Human Ear. 

CONTRARY to the general impression the transmis- 
sion of messages or words by radio does not consti- 
tute the sending of "sounds" but the passage of 
wave impulses which are in exact accord with every phase 
of the atmospheric waves produced by the voice. 

Scientists have long said that ' ' sounds do not exist ex- 
cept where there is someone to hear them." This of 
course means that wave motions of any sort, whether they 
be waves in the atmosphere or water, or the electric waves 
of radio, only exist so far as humans are concerned when 
the delicate ear vibrates in accordance with the wave mo- 
tions and the consequent sounds are conveyed to the 
brain. There are no sounds to the absolutely deaf man. 

The waves on entering the ear excite the sensation of 
sound ; the more rapid the vibrations the higher the pitch 
of the note or sound, and the greater the amplitude the 
louder the sound. The ear is especially adapted to re- 
ceive these vibrations and transform them into nervous 
impulses. In its construction it is divided into three parts 
for the purposes of simplified description. 

The outer ear consists of what the anatomists call the 
expanded pinna — which is really the external portion of 
the structure which all the world recognizes as "the ear," 
plus a tube along which the vibrations pass inward to the 
drum — scientifically known as the tympanic membrane, 

144 




T3 
<V 
t- 
V 

DO 

c 

* M 

o"~ 

Eg 

rf.2 
^ +5 

<j Mb 

5 ^ be 

fa *>.£ 

fa gg 

£ -^ 

H |.2 

3 a-. 



fa _§ 
^' >* s » 

fc Q ^ 

- fa e 2 

gtwc 

£ & »«~ 



Pi 
o 

o 



c 

o 
o 

(B C 



MIRACLE OF THE AGE 145 

Glands along the tube or canal secrete wax which guards 
the approach to the drum and protects it. As frequently 
happens, through injury or illness there is an inflamma- 
tion which interferes with the flow of the secretion and 
there is an excess of wax which hinders or prevents hear- 
ing and we send for an expert to remedy the condition — 
the physician or surgeon. 

The middle ear is called the tympanum, and is sepa- 
rated from the outer ear by the drum. The tympanum is 
a small cavity in the temporal bone of the skull communi- 
cating with the throat by the Eustachian tube. This tube 
is in reality a valve which controls the air pressure on the 
inside of the drum, which is exactly equal to the pressure 
on the external or outside under normal conditions. 

ALL SOUNDS ARE VIBRATIONS. 

The structures of the inner ear lie in the temporal bone 
on the side of the tympanum directly opposite the drum. 
They are made up of a system of small bony spaces and 
tubes called the bony labyrinth, inside of which is a corre- 
sponding membranous labyrinth. A part of this arrange- 
ment is called the cochlea, because it is shaped something 
like a curled shell or "conch." It resembles a snail's 
shell or spiral stairway. 

In the middle ear is a series of three small bones, con- 
stituting the ear ossicles, or what every schoolboy knows 
as the hammer, anvil and stirrup of the ear. The malleus 
(hammer) is attached to the drum membrane, next comes 
the incus (anvil) then the stapes (stirrup) which is joined 
to the membrane covering the fenestra ovalis or opening 
into the inner ear. These bones are held together by liga- 
ments and so arranged that when the sound waves set the 
tympanic membrane in vibration the motions are trans- 
mitted by the ossicles to the cochlea — of the inner ear. 
10 



146 KADIOTELEPHONY 

Part of the membranous labyrinth of the inner ear con- 
sists of two small sacs filled with a fluid, which themselves 
are surrounded by another fluid. Within the small sacs 
or bags are also tiny atoms of substance like fine sand 
which bounce up and down when wave vibrations are sent 
against the drum. To the membrane there extends from 
the brain a myriad of tiny nerves and through these 
nerves the movements of the tiny atoms, called otoconia, 
are transferred to the brain and we hear. 

Whenever we hear, therefore, there has been produced 
a vibration in some substance, whether it be a solid, a 
liquid or a gas — the ring of the bell, the splash of the 
water, the explosion of the gas. What really occurs is the 
passing out from the place in which sound originates of a 
rythmical motion of air particles. These motions mani- 
fest themselves in changes of pressure spreading out in 
enlarging circles or spheres through the atmosphere. 

MECHANISM OF SPEECH. 

The force that disturbs the atmosphere may produce 
almost any sort of vibration. The musical notes of an 
orchestra, and the notes of the individual instruments 
differ. When the fluctuations are regular they may be 
pleasing to the senses ; if irregular or intermittent they 
are to our trained senses " noise." 

The tuning fork has long been the favorite device used 
to demonstrate the fact that sound is produced by wave 
motions. When the fork is struck the tines or prongs 
vibrate for several seconds. The sounds produced by the 
vibrations are caused by wave motions set up in the at- 
mosphere. If a small wire or bristle is attached to the 
end of a tuning fork and during its period of vibration 
after being struck, it is drawn along a surface of smoked 
glass the trace of the fine wire or bristle will show a wavy 
line in the sooty coating. 



MIRACLE OF THE AGE 147 

The mechanism of our speech consists of a box in the 
throat called the larynx, across the top of which is spread 
two membranes, called vocal chords so arranged and con- 
trolled by muscles that their tension may be changed at 
will. When we breathe, the air passes between the chords 
to and from our lungs, and when we speak we tighten the 
muscles controlling the chords, and the edges of the 
chords are brought close together. They then vibrate 
because of the air passing between them, just as the reed 
in a clarionet or similar musical instrument may vibrate. 
The variations in tone are in accordance with the tense- 
ness of the chords and the amount of air which is forced 
between them. The tighter the chords the shriller the 
note because the vibrations are more rapid. Lower 
sounds and heavier notes are produced by lax chords. 

The control of these sounds in speech is through the use 
of the teeth, tongue, lips and the cavity of the mouth. It 
is no figure of speech to say that we create an atmospheric 
disturbance every time we talk. The wave motions we set 
up carry into the ear of our hearer and the little otoconia 
dancing around in the sacs in the inner ear in accordance 
with the vibrations on the drum of the ear telegraph the 
result into the brain — through the auditory nerve. 

In speaking into the telephone we talk against a thin 
metal plate which vibrates in accordance with the wave 
motions produced by the mouth and lips. The plate or 
diaphram vibrations are transmitted by force of electric- 
ity along the wire. The plate against which we talk does 
not itself transmit the sound, but its vibrations are 
changed into electric waves. 

Technically the sounds directed into the mouthpiece 
strike the diaphram, which causes pressure to be exerted 
upon a small cup containing particles of carbon. When 
these particles of carbon are loose and free they set up a 



148 EADIOTELEPHONY 

great resistance to the flow of electricity, but when they 
are compressed their resistance is lowered and they per- 
mit the electric current to flow. Thus the pressure 
exerted by the voice in speaking into the transmitter ac- 
tually is translated into terms of electricity. The varia- 
ion in pressure determines the flow of electricity and the 
consequent waves. 

THE TELEPHONE RECEIVER. 

The receiver consists of a thin metal disc, set close to 
the end of a magnetized bar of steel, which has around it 
a coil of insulated wire. The ends of the coil are attached 
to the wires attached to the battery and the transmitter, 
and the varying currents of electricity as produced 
through the pressure exerted in speech, generate similar 
changes in the magnetism of the receiving instrument, 
and by alternately repelling and attracting the diaphram 
vibrations are set up and given off as sounds. There are 
improvements in wire telephony but the principles in- 
volved are the same. 

Experiments have shown that the velocity of sound in 
the air is about 1,090 feet a second, but that in some liq- 
uids it is much greater — in water four times as great — 
while in inelastic substances like lead and wax it is very 
small, and in wood and steel very great, traveling at the 
rate of three or four miles per second. In order to be 
heard by the ear vibrations must be as numerous as 24 
per second — and they cannot exceed 30,000 to 40,000 per 
second. Above this point the vibrations are so rapid that 
they cease to produce any sensation upon the ear. 

The alternating current waves of radio, as has previ- 
ously been stated, are of such frequency — make so many 
oscillations per second — that they would not be audible 
to the ear, nor could they be heard with an ordinary tele- 



MIRACLE OF THE AGE 149 

phone receiver. Some form of rectifier was needed to so 
subdue the waves or slow them to a point that would make 
them audible before radio could be successful. 

It is perfectly obvious from the foregoing explanation 
that in order to have any sounds reach our ears there 
must be wave motions of some sort. Electricians found 
that the only sort of an electrical current that moved in 
waves was the alternating, and consequently it was the 
only form which could be used for wireless telephony. 

CURRENTS HAD TO BE RECTIFIED. 

The difficulties to be overcome were reducing the rapid 
wave motions to a point where the ear could hear them 
and so rectify the current as to make it a continuous wave, 
for in the alternating current the oscillations surge back 
and forth and were in the early attempts at radioteleph- 
ony found to be damped, as the electricians term it. In 
other words parts of the waves were lost and messages or 
signals came in broken waves that were only partly in- 
telligible. 

Eectifiers solved the problem. They turned the alter- 
nating waves into what is sometimes called continuous 
waves. Of the devices that helped solve the problem the 
electron tube, as originated by Fleming, De Forest and 
others, and described elsewhere, is the most efficient. 

With all the wonders of the radio, and what it is doing 
for us and the world at large, it cannot surpass the won- 
ders nor the efficiency of nature. What would we do if 
our ears were so sensitive that the wave motions stirred 
up in every city of the country — yes, and of the world — 
were audible to the naked ear! Who could stand it if the 
waves produced by the commotion in our own streets 
were carried to us in our homes at all times ? What if the 
motions stirred up everywhere had force enough behind 



150 EADIOTELEPHONY 

them to drive them around the world before they died into 
nothing? or what if the human ear were as sensitive as 
the * ' artificial ear ' ' which the radio experts and scientists 
have made for us f — f or after all the electron tube is prac- 
tically an artificial ear in the sense that it enables us to be 
conscious of wave motions set up in the ether that never 
were heard by man before. 



CHAPTER XVI. 

How to Make a Simple Receiving Set — Aerials — Details 
of Construction — Great Fun Receiving. 

HUNDREDS of combinations and arrangements 
have been devised in creating amateur receiving 
sets and an army of boys and girls are at work 
continuously building up ingenious contrivances out of 
which some excellent things are expected to develop. One 
of the great hopes of the future, according to the radio 
experts is the fact that thousands of youths are receiving 
a technical training, or some experience that will prove a 
benefit to the nation as a whole. 

Nearly every body has read some sort of a description 
of a small easily constructed receiving set and no one 
knows precisely which one of the devices may suddenly 
prove most efficient, but it is safe to assume that instruc- 
tions issued by the government for making a small radio 
receiving set may be regarded as efficient as any that can 
be produced at a relative cost. Those who wish to experi- 
ment therefore in an inexpensive way may accept the fol- 
lowing instructions as worthy of consideration, since they 
are based on a plan prepared by the United States Bureau 
of Standards for the Use of Boys' and Girls' Clubs. 

The station is designed to receive messages from me- 
dium power transmitting stations within a small radius 
arid high powered stations up to perhaps 50 miles, provid- 
ing the stations have wave lengths ranging from 200 to 
600 meters, though a greater distance may be covered at 
night. If they construct the coil and other parts as di- 
rected the cost of making the set may approximate $6, 

151 



152 EADIOTELEPHONY 

but if it is desired to make a more highly efficient set the 
price may mount to about $15. 

As outlined previously in the elementary chapter on 
equipment, the five essential parts are the aerial or an- 
tenna, lightning switch, ground connections, receiving set 
and phone. The latter may be either one or a pair of tele- 
phone receivers worn on the head of a listener. 

The antenna need be only a wire stretched between two 
elevated points. It should be not less than 30 feet above 
ground nor less than 75 feet long. It is well Jo have the 
furthest end from the house as high as possible. A lead-in 
wire — that is the wire running from the antenna to the 
house should drop as directly as possible into the light- 
ning switch. 

If the distance between the adjoining building or tree 
or pole should be greater than the 75 feet required for the 
antenna, the antenna can still be held to the required 
length by increasing the length of the anchor rope at the 
far end of the antenna. The rope anchorage at the end 
of the antenna next to the house should not be lengthened 
because it would necessitate the lengthening of the lead-in 
wire. The accompanying diagram will show how the an- 
tenna is attached. 

Details of Parts — The essential parts are hereafter 
mentioned by reference to the letters as shown in Dia- 
grams (Fig.) 1 and 2. 

A. and I. are screw eyes which must be strong enough 
to anchor the antenna at the ends. 

B. and H. are sections of rope % or % inch in diameter, 
just long enough to permit the antenna to swing clear of 
the two supports. 

D. is a piece of % or % inch rope of sufficient length to 
make the distance between the insulators E. and G. about 
75 feet. 



MIRACLE OF THE AGE 



153 



C. is a single block pulley thai may be used if readily 
available. 

The insulators E. and G. may be constructed of any 
hard wood strong enough to withstand the strain of the 
antenna. Blocks of IY2 x 2x10 inches will answer the pur- 
pose. Holes should be bored at either end far enough 
from the ends to give sufficient strength. If wood is used 
it is best to boil them in paraffin for about an hour. 




Porcelain wiring cleats may be used instead of the wood, 
if they are available, but if unglazed porcelain is used it 
should be boiled in paraffin the same as wood. 

The antenna is indicated by the letter F. suspended 
from or between the insulators E. and G. Either insu- 
lated or bare copper wire No. 14 or 16 may be used for 
the antenna. The end of the antenna furthest from the 
receiving set may be secured to the insulator E. by any 
substantial method, but great care should be used not to 
kink the wire. The other end of the antenna wire should 
be drawn through the insulator G. to a point where the in- 



154 EADIOTELEPHONY 

sulators are about 75 feet apart. The wire should be bent 
back and the insulator twisted to form a shank of the an- 
tenna as shown in Figure 1. The loose end of the antenna 
will be the drop or lead-in wire and should be just long 
enough to reach the lightning switch. 

K is the lightning switch. For the purpose of a small 
antenna this switch may be the ordinary porcelain-base, 
30 ampere, single-pole double-throw battery switch. 
These switches as ordinarily available, have a porcelain 
base about 1 by 4 inches. The " lead-in' ' wire (J) is at- 
tached to this switch at the middle point. The switch 
blade should always be thrown to the lower clip when the 
receiving set is not actually being used, and to the upper 
clip when it is desired to receive signals. 

L is the ground wire for the lightning switch; it may 
be a piece of the same size wire as used in the antenna, of 
sufficient length to reach from the lower clip to the light- 
ning switch (K) to the clamp on the ground rod (M). 

M is a piece of iron pipe or rod driven 3 to 6 feet into 
the ground, preferably where the ground is moist, and 
extending a sufficient distance above the ground in order 
that the ground clamp may be fastened to it. Scrape the 
rust or paint from the pipe before driving in the ground. 

N is a wire leading from the upper clip of the lightning 
switch through the porcelain tube (0) to the receiving set 
binding post marked ' i antenna. ' ' 

is a porcelain tube of sufficient length to reach 
through the window casing or wall. This tube should be 
mounted in the casing or wall so that it slopes down to- 
ward the outside of the building. This is done to keep 
the rain from following the tube through the wall to the 
interior. 

Fig. 2 shows the radio receiving set installed in some 
part of the house. 



MIRACLE OF THE AGE 



155 



P is the receiving set which is described in detail below. 

N is the wire leading from the ' ' antenna ' ' binding post 
of the receiving set through the porcelain tube of the 
upper clip of the lightning switch. This wire, as well as 
the wire shown by Q, should be insulated and preferably 




flexible. A piece of ordinary lamp cord might be un- 
braided and serve for these two leads. 

Q is a piece of flexible wire leading from the receiving 
set binding post marked "ground" to a water pipe, heat- 
ing system or some other metallic conductor to ground, 
except M, Fig. 1. If there are no water pipes nor radia- 
tors in the room the wire should be run out of doors and 
connected to a special " ground' ' below the window, which 



156 RADIOTELEPHONY 

shall not be the same as the "ground" for the lightning 
switch. It is essential that for the best operation of the 
receiving set this "ground" be of the very best type. If 
the soil near the house is dry it is necessary to drive one 
or more pipes or rods sufficiently deep to encounter moist 
earth and connect the ground wire to the pipes or rods. 
This distance will ordinarily not exceed six feet. Where 
clay soil is encountered this distance may be reduced to 
three feet, while in sandy soil it may be increased to ten 
feet. If some other metallic conductor, such as the casing 
of a drilled well, is not far away from the window, it will 
be a satisfactory ' ' ground. ' ' 

TUNER, DETECTOR AND PHONE. 

The detector and phone will have to be purchased. The 
tuner and certain accessories can be made at home. 

Tuner (E, Fig. 3) — This is a piece of cardboard or 
other nonmetallic tubing with turns of copper wire wound 
around it. The cardboard tubing may be an oatmeal box. 
Its construction is described in detail below. 

Crystal Detector (S, Fig. 3) — The construction of a 
crystal detector may be of very simple design and quite 
satisfactory. The crystal, as it is ordinarily purchased 
may be unmounted or mounted in a little block of metal. 
For mechanical reasons the mounted type may be more 
satisfactory, but that is of no great consequence. It is 
very important, however, that a very good tested crystal 
be used. It is probable also that a galena crystal will be 
more satisfactory to the beginner. 

The crystal detector may be made up of a tested crystal, 
the wood screws, short piece of copper wire, a nail, set- 
screw type of binding post, and a wood knob or cork. 
The tested crystal is held in position on the wood base by 
brass wood screws as shown at 1, Fig. 3. A bare copper 



MIRACLE OF THE AGE 



157 



wire may be wrapped tightly around the three brass 
screws for contact. The assembling of the rest of the 
crystal detector is quite clearly shown in Fig. 3. 




Phone (T, Fig. 3) — It is desirable to use a pair of 
telephone receivers connected by a head band, usually 
called a double telephone headset. The telephone re- 
ceivers may be any of the standard commercial makes 
having a resistance of between 2,000 and 3,000 ohms, 



158 RADIOTELEPHONY 

The double telephone receivers will cost more than all 
the other parts of the station combined, bnt it is desirable 
to get them, especially if one plans to improve his re- 
ceiving set later. If one does not care to invest in a set of 
double telephone receivers, a single telephone receiver 
with a head band may be used ; it gives results somewhat 
less satisfactory. 

Accessories — Under the heading of accessory equip- 
ment may be listed binding posts, switch arms, switch 
contacts, test buzzer, dry battery, and boards on which 
to mount the complete apparatus. The binding posts, 
switch arms, and switch contacts may all be purchased 
from dealers who handle such goods, or they may be 
quite readily improvised at home. There is nothing 
peculiar about the pieces of wood on which the equipment 
is mounted. They may be obtained from a dry packing- 
box and covered with paraffin to keep out moisture. 

DETAILS OF CONSTRUCTION. 

The following is a detailed description of the method 
of winding the coil, construction of the wood panels, and 
mounting, and wiring the apparatus. 

Tuner — See R, Fig. 3. Having supplied oneself with 
a piece of cardboard tubing 4 in. in diameter and about 
1-2 pound of No. 24 (or No. 26) double cotton-covered 
copper wire, one is ready to start the winding of the tuner. 
Punch two holes in the tube about 1-2 in. from one end 
as shown at 2, Fig. 3. Weave the wire through these 
holes in such a way that the end of the wire will be firmly 
anchored, leaving about 12 inches of the wire free for 
connections. Start with the remainder of the wire to 
wrap the several turns in a single layer about the tube, 
tightly and closely together. After 10 complete turns 
have been wound on the tube hold those turns snugly 



MIRACLE OF THE AGE 159 

while a tap is being taken off. This tap is made by mak- 
ing a 6 in. loop of the wire and twisting it together at 
such a place that it will be slightly staggered from the 
first tap. This method of taking off taps is shown quite 
clearly at U, Fig. 3. Proceed in this manner until 7 
twisted taps have been taken off at every 10 turns. After 
these first 70 turns have been wound on the tube then 
take off 6 inches twisted tap for every succeeding single 
turn until 10 additional turns have been wound on the 
tube. After winding the last turn of wire anchor the 
end by weaving it through two holes punched in the tube 
much as was done at the start, leaving about 12 in. of 
wire free for connecting. It is understood that each of 
the 18 taps is slightly staggered (or stepped away) from 
the one just above, so that the several taps will not be 
bunched along one line on the cardboard tube. See Fig. 
3. It would be advisable, after winding the tuner as just 
described, to dip the tuner in hot paraffin. This will help 
to exclude moisture. 

Upright Panel and Base — Having completed the 
tuner to this point, set it aside and construct the upright 
panel shown in Fig. 4. This panel may be a piece of 
wood approximately 1-2 in. thick. The position of the 
several holes for the binding posts, switch arms and 
switch contacts may first be laid out and drilled. The 
"antenna" and "ground" binding posts may be ordi- 
nary 1-8 in. brass bolts of sufficient length and supplied 
with three nuts and two washers. The first nut binds 
the bolt to the panel, the second nut holds one of the short 
pieces of stiff wire, while the third nut holds the antenna 
or ground wire as the case may be. The switch arm 
with knob shown at V, Fig. 3, may be purchased in the 
assembled form or it may be constructed from a thin 
slice cut from a broom handle and a bolt of sufficient 



160 



EADIOTELEPHONY 



length equipped with four nuts and two washers, together 
with a narrow strip of thin brass somewhat as shown. 
The switch contacts (W, Fig. 3) may be of the regular 
type furnished for this purpose or they may be brass 
bolts equipped with one nut and one washer each, or 
they may even be nails driven through the panel with an 




individual tap fastened under the head or soldered to 
the projection of the nail through the panel. The switch 
contacts should be just enough that the switch arm will 
not drop between the contacts, but also far enough apart 
that the switch arm can be set so as to touch only one 
contact at a time. 

The telephone binding post should preferably be of the 
set screw type as shown at X, Fig. 3. 

INSTRUCTIONS FOR WIRING. 

Having constructed the several parts just mentioned 
and mounted them on the wood base, one is ready to 
connect the several taps to the switch contacts and attach 




2 a 







^ o 






fc-o 






-o >> 






<u *h 






-M nS 






c d 












>T3 




Q 


.5 O 




tf 


m g 







^rt 






Si 




X 






H 


*?& 




g 


2^ 




H 








• 43 >> 











Q 


«s«« 




«4 


cj w~3 




H 


.H~S 










J 


. < 


M 2. W 


o 



7. 


0) 


P 


fc 


*f5fl 


> 


(4 

■s s § 


4 




2 5+3 


-a 




%»?> 


o 




" S c 













^ 








P 




O t- qj 






W M +-> 








f, 




^ri° 


~ 




•c £^ 


ft 




k«g 







® - 


O 




££ 








6^5 






s g 'S 




£ 




o 


«C^ 







© 05 J- 

»6| 




3 






m 




< 


0) ^rt 




* 


£.2o 




O 


lis 




Eh 


O «} 




£.S£>, 






*h O ^ 




o 


-cs+i 






ftm w C 




S 


^ w w o 




<< 


og^o 




p^ 

H 






w 


cL^ 




Eh 


h 32 




> 




O 






00 


*§*5 




Z 


56 2& 






+-> O M 




Eh 


+j +-> ft <B 

09 ^r; 

.5~.2 




< 


-,H <$'<£ bo 




H 
w 








K fl a) W 






t; > a? o 

"S.P > >- 


« 


o G S fi 
S s r; p. 


o 


> 


o 


O 
O 






H 




3 


DQ 


o 


o 


ih'OoO 


o 


K 


OC> 


■a 


£ 
£ 










to 




2 rtO+j 


"2 


H 


£*-£ ® 






« 09 


o 




a> • .!-< 


U 




wEh-C 




^O 
ricj S £> 

<u C 0) 
ti o w s_ 
G s- o> o 

G L w 

g g^ c 

.G^ fit) 

&?a, ft a; §> 
m h <d S ° 

°«| ftO 

■t5 +-> ^ -t_> 
rt G <" 

£ as oU 



rt 73 <D vi G 
<u -^ >> 0> o 

^-o ^ &CG 

g*-y wwrt 

O G 01 •>-»-> 

eSoJL 

©ft hi "Si 

2h> * 

•> ""< en 4> 










60° 

d m p< 
N +-> o> 

M 4) ^ 

2 0*0 
go* 

<! rt-d 

a*S 

3 5?" 



v > <x> o 

°8§3 

"O ^IT-I 

f" c " ~ 

3* 



is o 



43 
to 

"S 

>> 
ft 
o 
U 



0> <B W^H 
•° ^ M G O 

G*Sb« 

^ rti$fl'0 



O K 



2-2^ g£? 

£ _, ■*"* -rt '*-> 

1.2.15 



MIRACLE OF THE AGE 161 

the other necessary wires. Scrape the cotton insulation 
from the loop ends of the sixteen twisted taps as well as 
from the ends of the two single taps coming from the first 
and last turns. Fasten the bare ends of these wires to the 
proper switch contacts as shown by the corresponding 
numbers in Fig. 3. One should be careful not to cut or 
break any of the looped tags. It would be preferable to 
fasten the connecting wires to the switch contacts by bind- 
ing them between the washer and the nut as shown at 3, 
Fig. 3. A wire is run from the back of the binding post 
marked "ground" (Fig. 3) to the back of the left-hand 
switch-arm bolt (Y), thence to underneath the right-hand 
binding post marked " phones/ ' to underneath the bind- 
ing post (4, Fig. 3) which forms a part of the crystal de- 
tector. A piece of No. 24 bare copper wire about 2 1-2 
in. long, one end of which is twisted tightly around the 
nail (the nail passing through binding post 4), the other 
end of which rests gently by its own weight on the crystal. 
(1). The bare copper wire which was wrapped tightly 
around the three brass wood screws holding the crystal 
in place is led to and fastened at the rear of the right- 
hand switch arm bolt (V), thence to the upper left-hand 
binding post marked "antenna." As much as possible 
of this wiring is shown in Fig. 3. 

DIRECTIONS FOR OPERATING. 

After all the parts of this crystal-detector radio receiv- 
ing set have been constructed and assembled the first es- 
sential operation is to adjust the little piece of wire, 
which rests lightly on the crystal, to a sensitive point. 
This may be accomplished in several different ways ; the 
use of a miniature buzzer transmitter is very satisfactory. 
Assuming that the most sensitive point on the crystal has 
been found by method described in paragraph below, 



162 EADIOTELEPHONY 

1 ' The Test Buzzer, ' ' the rest of the operation is to get the 
radio receiving set in resonance or in tune with the sta- 
tion from which one wishes to hear messages. The tun- 
ing of the receiving set is attained by adjusting the induc- 
tance of the tuner. That is, one or Both of the switch 
arms are rotated until the proper number of turns of 
wire of the tuner are made a part of the metallic circuit 
between the antenna and ground, so that together with 
the capacity of the antenna the receiving circuit is in reso- 
nance with the particular transmitting station. It will 
be remembered that there are 10 turns of wire between 
each of the first 8 switch contacts and only one turn of 
wire between each 2 of the other contacts. The tuning 
of the receiving set is best accomplished by setting the 
right-hand switch arm on contact (1) and rotating the 
left-hand switch arm over all its contacts. If the desired 
signals are not heard, move the right-hand switch arm to 
contact (2) and again rotate the left-hand switch arm 
throughout its range. Proceed in this manner until the 
desired signals are heard. 

It will be advantageous for the one using this radio 
receiving equipment to find out the wave frequencies 
(wave length) used by the several radio transmitting sta- 
tions in his immediate vicinity. 

The Test Buzzer (Z, Fig. 3) — As mentioned previously, 
it is easy to find the more sensitive spots on the crystal 
by using a test buzzer. The test buzzer is used as a min- 
iature local transmitting set. When connected to the 
receiving set as shown at Z, Fig. 3, the current produced 
by the buzzer will be converted into sound by the 
telephone receivers and the crystal, the loudness of the 
sound depending on what part of the crystal is in contact 
with the fine wire. To find the most sensitive spot con- 
nect the test buzzer to the receiving set as directed, close 



MIRACLE OF THE AGE 163 

the switch (5, Fig. 3) (and if necessary adjust the buzzer 
armature so that a clear note is emitted by the buzzer), 
set the right-hand switch arm on contact point No. 8, 
fasten the telephone receivers to the binding posts 
marked "phones," loosen the set screw of the binding 
post slightly and change the position of the fine wire 
(6, Fig. 3) to several positions of contact with the crystal 
unit until the loudest sound is heard in the phones, then 
tighten the binding post set screw (4) slightly. 

APPROXIMATE COST OF PARTS. 

The following list shows the approximate cost of the 
parts used in the construction of this radio receiving 
station. The total cost will depend largely on the kind 
of apparatus purchased and on the number of parts con- 
structed at home. 

Antenna — 

Wire — Copper, bare or insulated, No. 14, 100 to 150 

feet, about 75 

Rope — y§ or y 2 inch. 2c per foot. 

2 insulators, porcelain 20 

1 pulley 15 

Lightning switch — 30 ampere battery switch 30 

1 porcelain tube 10 

Ground connections — 

Wire (same kind as antenna wire.) 

1 clamp 15 

1 iron pipe or rod 25 

Receiving set — 

Yz pound No. 24 copper wire double cotton-covered ... .75 

1 cardboard box. 

2 switch knobs and blades complete 1.00 

18 switch contacts and nuts 75 

3 binding posts — set screw type 45 

2 binding posts — any type 30 

1 crystal — tested 25 

3 wood screws, brass, y A in. long 03 

Wood for panels (from packing box.) 

2 pounds paraffin , 30 



164 KADIOTELEPHONY 

Lamp cord, 2 to 3c per ft. 

Test buzzer 50 

Dry battery 30 

Telephone receivers 4.00 to $ 8.00 

Total $11.00 $15.00 

If nothing but the antenna wire, lightning switch, 
porcelain tnbe, crystal, telephone receiver, bolts and 
buzzer are purchased this total can be reduced to about 
$6.00. 

Sets of the kind described above cannot be used satis- 
factorily with a loud talker; that is an amplifying horn 
or similar device for making the messages audible in an 
open room, but for individual use, where the set is suf- 
ficiently sensitive to catch the music or message of the 
air the amateur can have lots of fun and learn much. 

Many cheaper devices (sets) have been constructed 
for receiving short distance waves. In one recently de- 
scribed set a boy used an ice cream container of pressed 
paper, with brass paper fasteners for switch contacts 
and succeeded in making the entire set at a cost of a 
couple of dollars. Such sets however are mere toys and 
it would be impossible to build them up or develop them 
into anything of much greater efficiency. 



CHAPTER XVII. 

Radio in the World War — Radio Control and Direction 
of Ships at Sea — Airplanes Directed from Land. 

HOW the radio enabled the British Navy to locate 
the Grerman war fleet and follow its movements 
jnst before the battle of Jutland is one of the pic- 
turesque and thrilling incidents of the World War which 
will go down in history to prove the value of the wonder- 
ful wireless as an aid to man in his warfare against his 
enemies. 

The marvelous "loop" antenna, now identified by 
nearly everybody as part of the equipment which may be 
used to make up a receiving set in radiotelephony was 
the magic device which enabled the British to trace the 
German war vessels and give battle to the latter 's dis- 
advantage. 

When the instructions from the German flagship were 
sent by wireless to the vessels of the fleet, the message 
was heard at several of the English stations along the 
British coast and the bearings of the German vessel giving 
the signals were accurately determined. A little later, 
the same vessel wired another lot of instructions and the 
English stations again determined the bearings of the 
vessel. These locations showed that the German vessel 
had moved about seven miles down the river. This was 
recognized as of sufficient importance by Sir H. B. Jack- 
son, the First Sea Lord, to justify ordering out the 
British Grand Fleet and clearing the North Sea, with the 
result that the British were able to pursue the Germans 
even before they were really at sea. The "loop" made 

165 



166 KADIOTELEPHONY 

it possible for the British to locate and anticipate the 
action of the Germans. 

Prior to the war the public knew but little about the 
almost idolized "loop," which on shipboard has some- 
times been called a "Eadio compass" or a "direction 
finder." The ships at sea determine their positions by 
listening to the signals sent from what are termed ' ' radio 
compass" stations along the coast, and during the war 
the mysterious messages carried on ether waves served 
battleships, torpedo boats and passenger steamships 
during many tense moments in the darkness of the night. 

The use of the loop, or radio compass, to direct assist- 
ance to a wrecked ship at sea and to guide a vessel into 
port through fog or storm, is now regarded as its most 
valuable field of usefulness. The neighboring ship may 
be located in the fog and passed in safety. Eadio sta- 
tions on the coast may direct the oncoming vessel, which 
with a radio finder may follow a true course. Life boats 
adrift in fog or storm, if equipped with even the simplest 
type of transmitting apparatus, could be located and 
picked up and those on board saved. "Wherever it is 
necessary for one vessel to locate another under any con- 
dition the finder or compass can be used to solve the 
problem. 

It was the wireless stations along the coast which gave 
warning during the tense period of the war of the ap- 
proach of the German submarines to our coast, and it was 
the call of the wireless operator that summoned the tor- 
pedo boat destroyers and chasers to protect passenger 
steamships when German raiders were at work on the 
high seas. Hundreds, yes, thousands of lives were saved 
by the wireless operators along the shores of England, 
France and America. 



MIRACLE OF THE AGE 167 

Most of this work was actually done by the wireless 
telegraph, for the radiophone did not actually come into 
its own until the end of the war — until in actual fact 
broadcasting began. But the radiophone was actually in 
existence and was used by the Signal Corps and other 
branches of the government service long before the pub- 
lic took it up as an amusement and a study, and one of the 
early public demonstrations was that in which Secretary 
Daniels of the Navy talked from the ground to the pilot 
of a seaplane in mid-air. 

RADIO IN THE WAR. 

The "direction finder 7 ' or loop was proved of great 
value on the seas long before the great bulk of the people 
had any idea of its existence, and before the close of the 
war it was shown that the same possibilities that are open 
to vessels in determining direction and getting their bear- 
ings by its use, apply in the case of aircraft. 

The type of finder generally used on shipboard is that 
of the wooden frame shaped like the letter X, and wound 
with wire as previously described. In connection with 
its use the United States Bureau of Standards has de- 
veloped a system in which the finder on shipboard is so 
connected with a radio receiving set that when the finder 
in picking up the ether sound waves is turned upon its 
axis the direction from which the message or signal 
comes is indicated either on the card of a magnetic com- 
pass or is read and determined according to a fixed scale. 

Another type of finder was, however discovered by 
General Squier in connection with his development of 
"wired wireless.' ' It is a consonance wave coil — a wire 
closely wound around a tube or core about four inches in 
diameter and two feet long. Over the coil is a metal ring 
connected to the grid of the electron tube of a receiving 



168 EADIOTELEPHONY 

set, constituting what is known to radio students as a 
capacity coupling. With this coil, or as it has been termed 
"dividing rod," the source of ether waves may actually 
be determined, and it can be used not only as a direction 
finder, but as a tuner and as an antenna. 

RADIO STEERS BATTLESHIP. 

As a matter of public interest the United States 
Government through various branches of service has 
done more to advance radio than any other country. The 
Army and Navy are steering airplanes and seaplanes 
without pilots by radio, and steering the course of ships 
by wireless from afar. 

In April, 1922, the grand old battleship Iowa, having 
ended its days of usefulness as a fighting machine, was 
sent out of the Philadelphia Navy Yard to a watery grave 
under its own steam, and directed and guided by radio. 
The big ship went to serve as a target for the Atlantic 
fleet off the coast near Cape Henry, there to be sunk by 
the shells from sister ships. 

The Iowa was built in 1893, and for a long time was the 
crack ship of the navy. i i Fighting Bob ' ' Evans was its 
commander at the battle of Santiago, when the Spanish 
Cape Verde fleet, under Admiral Cervera was destroyed 
without the loss of an American vessel. 

At one time there was talk of selling the Iowa to 
Greece, along with the Lemnos and Kilkis, formerly 
Idaho and Mississippi. With the outbreak of the World 
War the Iowa was used as " coast patrol battleship No. 
4," its crew being made up of naval reserves. 

The radio control installed in it is the invention of 
John Hays Hammond, Jr., who has achieved success with 
wireless controlled torpedoes and small craft. Although 
secret, the device is known to be in the form of a seg- 



MIRACLE OF THE AGE 169 

mented disc, each segment of which sends ont a different 
radio "wave" or signal. On board the controlling ship, 
which keeps several miles distant, is a similar disk. Each 
segment controls some piece of apparatus aboard the 
Iowa, and is brought into nse much as a motorman by 
turning his controller handle utilizes different speeds for 
a trolley car. 

Thus one segment may control the throttle which gives 
steam to the battleship's engines, while another may re- 
verse the engines. Each segment aboard the ship only 
responds to its own particular wave or signal through the 
atmosphere. In addition to this, by automatic devices, 
the Iowa by radio informs those aboard the distant con- 
trolling ship of whether more fuel is needed, what the 
steam pressure is, etc. 

GUIDE TORPEDOES BY WIRELESS. 

Accurate drawings and the possible existence of du- 
plicates of this intricate apparatus insure that radio 
control of battleships shall remain for the navy despite 
the sinking of the first example of it. 

Uncle Sam is similarly guiding torpedoes through the 
water by radio and in an experimental way is communi- 
cating with submarines under water. The Navy alone 
has more than fifty radio compass, or beacon radio sta- 
tions along the coast and its island possessions, and 
during 1921 bearings were given to upward of 25,000 
vessels at sea. This does not include the stations and the 
operations of the Lighthouse Service. In addition to the 
beacon stations there are about 600 Naval ship stations, 
Naval airplane and shore radio stations. Moreover the 
Army has a very complete radio service through which 
it connects and can communicate with all of its artillery, 
aviation and other posts and in cooperation with the 



170 KADIOTELEPHONY 

Navy service and organization can cover the whole coun- 
try and transact Trans-Atlantic business as well. 

The Post Office Department is using wireless in connec- 
tion with the air mail service and the Department of 
Commerce which controls the licensing of all sending sta- 
tions is one of the most active agents in the development 
of radio that the country affords. 

The relation of radio to the Government is even not 
indicative of the possibility that hereafter not humans, 
but radio operated mechanical devices will form the basis 
of our combatant forces on the sea and in the air and 
perhaps on the land. 

It does not require a great stretch of imagination to 
make it seem possible that if warships and airplanes can 
be directed and controlled from afar, even to the point 
of fueling the engines, putting water in the boilers and 
turning the great guns to point of action, the same thing 
may be true of the big caterpillar tanks that proved such 
effective weapons of offense and defense during the war. 
And could not great guns be fired by radio, torpedoes 
launched and every other activity directed from airplanes 
in the sky or shore radio stations ? 

AMERICA BUILT FRENCH RADIO STATION. 

It is significant, too, that the greatest radio station in 
France — The Lafayette — was constructed by Uncle Sam 
during the World War. The truth is that while the big 
telephone and electric companies did a great deal to de- 
velop radio and visualize its possibilities by establishing 
radio stations, the United States Navy actually did the 
first broadcasting from its Naval Air Station at Anacos- 
tia, near Washington. 

The United States Coast Guard, too, has incorporated 
the radiotelephone in its service equipments and has in- 



M1EACLE OF THE AGE 171 

stalled radio sets in its boats so that direct communica- 
tion may be bad with the shore. In developing the idea 
a test was made at Atlantic City where one life boat was 
able to talk to the shore station at a distance of six miles 
out at sea. A receiving and transmitting set were in- 
stalled well forward in the boat and the connections were 
so arranged as to make the steel keel of the boat serve as 
sort of an antenna. 

The United States Public Health Service, too, is using 
the radio and where there is no physician on board a 
ship at sea and medical service is required, emergency 
instructions are sent by wireless. The Seaman's Church 
Institute, N. Y., was one of the first institutions to utilize 
the radio for this purpose, and the Department of Com- 
merce quickly granted the institution a special commer- 
cial license for radio sending. Arrangements were made 
with a New York City Hospital to furnish essential med- 
ical directions and service was rendered to persons ill 
on a number of vessels. The work proved so valuable 
that the Public Health Service has taken up the work to 
develop a complete Marine medical service from stations 
all along the coast. 



CHAPTEE XVIII. 

Kadio Regulation — Government Control in Peace and 
War — Rules. 

ONE of the difficult problems presented by the spread 
of the " radio craze' ' is that which had to do with 
the regulation by the Government of all forms of 
wireless communication. In England private individuals 
were not permitted to have radios during the war, or 
operate them, and as the order was not rescinding after 
peace was declared the popular use of the wireless has 
not kept pace with that in America. 

Here anyone has been permitted to have a wireless and 
the restrictions have principally been directed toward 
the sending of messages and the length of the waves 
which amateurs might use. So when the demand for the 
radiophone swept over the country and the use grew 
from a few thousands into millions the United States 
Government found itself swamped in its attempts to meet 
the situation. 

The office of W. D. Terrell, Chief Eadio Inspector for 
the Government in Washington, was figuratively speak- 
ing flooded overnight with applications for licenses to 
operate wireless machines, and install broadcasting sta- 
tions. Enthusiasts wrote for information and hundreds 
of complaints were received from persons who objected 
to having the messages and music received from large 
broadcasting stations, interfered with by unimportant 
wave messages sent out by some amateur who selected 
the same length of waves as that the larger station hap- 
pened to be using. 

172 



MIRACLE OF THE AGE 173 

The wireless telegraph has of course been in use for a 
score of years and when the rules for wireless operation 
were originally drafted they were intended to govern 
radiotelegraphy — there was no radiophone. The coun- 
try was dotted over with amateur operators who fre- 
quently amused themselves by relaying messages from 
one to another all across the United States. Some of 
these amateurs were very efficient and belonged to the 
National Amateur Wireless Association which main- 
tained a national traffic organization to relay messages 
across country without charge. 

During the war all of these stations were under close 
inspection, but the force of inspectors and those whose 
duty it is to deal with wireless operation for the Govern- 
ment did not keep pace with the increased volume of busi- 
ness and problems presented themselves faster than they 
could be solved. 

The big problem already referred to — that of regulat- 
ing or restricting the use of wave lengths so as to prevent 
interference — grew into a great National and Interna- 
tional question and a general conference was held in 
Washington to adopt some plan of regulation for the 
United States. 

The conference was held at the Department of Com- 
merce in Washington, by members of a Eadio Commis- 
sion appointed by Secretary Hoover, and consisting of 
Dr. S. W. Stratton, chairman, director of the Bureau of 
Standards of the Department of Commerce. Major- 
General George 0. Squier, of the War Department ; Capt. 
S. W. Bryant, U. S. N. ; J. C. Edgerton, Superintendent 
Radio Service, Post Office Department; W. A. Wheeler, 
Bureau of Markets and Crop Estimater, of the Depart- 
ment of Agriculture ; Wallace H. White, Jr., of Maine ; 
R. B. Howell, Omaha ; Dr. Alfred N. Goldsmith, Secre- 



174 EADIOTELEPHONY 

tary Institute Eadio Engineers, N. Y. ; Hiram P. Maxim, 
American Eadio Eelay League, Hartford; Prof. L. A. 
Hazeline, Stevens Institute, Hoboken; D. B. Carson, 
Commissioner of Navigation, Department of Commerce ; 
Prof. C. M. Janshy, University of Minnesota, and Edwin 
H. Armstrong, of Columbia University. 

SECRETARY HOOVER ON RADIO. 

The principal recommendation of the commission had 
to do with the allocation of twenty bands of waves be- 
tween 150 to 6,000 meters in length and the suggestion 
that control and regulation of the radio be vested in the 
Department of Commerce and that radio telephony be 
given the status of a public utility. 

Secretary Hoover in his address to the commission 
outlined the situation in a way that shows what the 
Government regards as essential and is interesting. In 
essence Secretary Hoover said : — 

"We are indeed today upon the threshold of a new 
means of widespread communication of intelligence that 
has the most profound importance from the point of view 
of public education and public welfare. The compara- 
tive cheapness with which receiving stations can be in- 
stalled, and the fact that the genius of the American boy 
is equal to construction of such stations within the limits 
of his own savings, bid fair to make the possession of 
receiving sets almost universal in the American home. 

* ' I think that it will be agreed at the outset that the use 
of the radiotelephone for communication between single 
individuals as in the case of the ordinary telephone is a 
perfectly hopeless notion. Obviously if ten million 
telephone subscribers are crying through the air for their 
mates they will never make a junction ; the ether will be 
filled with frantic chaos, with no communication of any 



MIRACLE OF THE AGE 175 

kind possible. In other words, the wireless telephone has 
one definite field, and that is for spread of certain pre- 
determined material of public interest from central sta- 
tions. This material must be limited to news, to educa- 
tion, to entertainment, and the communication of such 
commercial matters as are of importance to large groups 
of the community at the same time. 

"It is therefore primarily a question of broadcasting, 
and it becomes of primary public interest to say who is to 
do the broadcasting, under what circumstances, and with 
what type of material. It is inconceivable that we should 
allow so great a possibility for service, for news, for en- 
tertainment, for education, and for vital commercial pur- 
poses, to be drowned in advertising chatter, or for com- 
mercial purposes that can be quite well served by our 
other means of communication. 

WHY STATIONS WERE LICENSED. 

"Congress some few years ago authorized the Secretary 
of Commerce to license radio sending stations, and to im- 
pose certain conditions in the licenses designed to prevent 
interference between the stations and to serve the public 
good. This legislation was drawn before the development 
of the telephone was of consequential importance. Until 
the last four or five months there has been but little 
difficulty in handling these regulations, because sending 
purposes have been largely confined to radiotelegraph, 
and to a very small extent to the radiotelephone. The 
extraordinary development of the radiotelephone, how- 
ever, has brought us face to face with an entirely new 
condition upon which licenses should be issued. It raises 
questions to to what extension in the powers of the de- 
partment should be requested of Congress in order that 
the maximum public good shall be secured from the de- 



176 EADIOTELEPHONY 

velopment of this great invention. During the last five 
months, while this extraordinarily rapid installation has 
been in progress, I and my colleagues in this department 
have seen that we should take a very conservative atti- 
tude on the issuance of sending licenses and I am able to 
inform you that there are today, outside of government 
broadcasting stations and the field authorized to the 
American boy, but few licenses outstanding — and these 
are limited to a small proportion of the number of the 
available wave lengths. We have therefore kept the field 
clear for constructive development. The experience 
gained indicates that the time has arrived not only when 
this large mass of subscribers need protection as to the 
noises which fill their instruments, but also when there 
must be measures to stop the interferences which have 
already grown up between even the limited number of 
sending stations which threaten to destroy them all. 

c l The problem is one of most intensely technical charac- 
ter, but is not one without hope of fairly complete solu- 
tion. Fortunately, the sending of radiotelephone mes- 
sages can be arranged in wave lengths sufficiently far 
apart so as not to interfere with each other, and receivers 
can at their option tune their receiving instruments to the 
different wave bands. With the improvement in the art 
and in the delicacy of instruments, the distance between 
wave lengths may eventually decrease and thus the num- 
ber of layers of messages increase. Furthermore, it is 
possible to increase the number of sending stations and 
thus the variety of material, if the power applied to cer- 
tain wave lengths is limited so as to circumscribe the area 
of distribution from a given station. Beyond this again 
certain times a day may be set aside within certain wave- 
lengths for certain types of information. 

1 'With the permutations possible to work out in differ- 



MIRACLE OF THE AGE 177 

ent wave lengths, in different geographical areas, in dif- 
ferent times of day, we should be able to make it possible 
for the owner of a receiving instrument, by tuning his 
instrument to different wave lengths, at different times, to 
possess himself of a great variety of entertainment, in- 
formation, news, etc., at his own option. Even if we use 
all the ingenuity possible I do not believe there are 
enough permutations to allow unlimited numbers of send- 
ing stations. 

MUST LIMIT SENDING STATIONS. 
* ' One of the problems that enter into this whole question 
is that of who is to support the sending stations. In cer- 
tain countries, the government has prohibited the use of 
receiving instruments except upon payment of a fee, out 
of which are supported government sending stations. I 
believe that such a plan would most seriously limit the 
development of the art and its social possibilities and 
that it is almost impossible to control. I believe that we 
ought to allow anyone to put in receiving stations who 
wishes to do so. But the immediate problem arises of 
who will do the broadcasting, and what will be his pur- 
pose. It is at once obvious that our universities, our tech- 
nical schools, our government bureaus, are all of them 
willing and anxious to distribute material of extremely 
valuable order without remuneration. Also judging 
from the applications we have had, any number of mer- 
chants are prepared to distribute entertainment pro- 
vided they are allowed to interlard discussion as to the 
approaching remnant sale. Many of the larger news- 
paper publishers are asking for licenses to install broad- 
casting sets in which news and entertainment will be dis- 
tributed, and the commercial companies are requesting 
licenses for the establishment of systematic distribution 
of news and entertainment conditional upon their being 
12 



178 EADIOTELEPHONY 

given permission to undertake commercial broadcasting 
of one kind or another. 

CAN ACCOMMODATE DEMANDS. 

"It is my belief that, with the variations that can be 
given through different wave lengths, through different 
times of day, and through the staggering of stations of 
different wave lengths in different parts of the country it 
will be possible to accommodate the most proper demands 
and at the same time to protect that precious thing — the 
American small boy, to whom so much of this rapid ex- 
pansion of interest is due. 

1 ' It is, however, a problem of regulation, if we are to get 
the maximum use. It is one of the few instances that I 
know of where the whole industry and country is earnest- 
ly praying for more regulation. Eegulation will need to 
be policed, if there is not to be great prejudice to the 
majority, and thus the celestial system — at least the ether 
part of it — comes within the province of the policeman. 
Fortunately the art permits such a policeman by listening 
in to detect those ether hogs that are endangering the 
traffic. 

"There is involved, however, in all of this regulation 
the necessity to so establish public right over the ether 
roads that there may be no national regret that we have 
parted with a great national asset into uncontrolled 

bands.' ' 

As an evidence of the necessity for control on the part 
of the Government it was stated that if all the Depart- 
ment stores in the United States were to request permis- 
sion to install transmission or broadcasting stations there 
would not be enough waves to go around. 

The general recommendations as to the allocation of 
waves were: — 



MIRACLE OF THE AGE 179 

Below 150 meters — Keserved. 

150 to 200 meters — Amateurs, exclusive. 

200 to 275 meters — Schools and amateurs. 

275 to 285 meters — Police broadcasting. 

310 meters — Special amateur telegraphy. 

310 to 435 meters — Private and toll broadcasting. 

500 to 525 meters — Aircraft telephony and telegraphy. 

525 to 650 meters — Mobile radiotelephony. 

650 to 700 meters — Mobile radiotelephony. 

700 to 750 meters — Government and public broadcasting, 700 miles 
inland. 

750 to 800 meters — Radio compass, exclusive. 

850 to 950 meters — Aircraft telegraphy and telephony. 

950 to 1050 meters — Eadio beacons, exclusive. 
1050 to 1500 meters — Government and public broadcasting. 
1500 to 1550 meters — Aircraft telephony and telegraphy. 
1550 to 1650 meters — Fixed stations, nonexclusive. 
1850 to 2250 meters — Government broadcasting, nonexclusive. 
2500 to 2660 meters — Mobile service, nonexclusive. 
2850 to 3300 meters — Fixed service, radiotelephony. 
5000 to 6000 meters — Trans-oceanic radiotelephone experiments. 

GOVERNMENT RULES AND REGULATIONS. 

The original Government rules and regulations for 
radio operation provide : — 

The owner of an amateur radio transmitting station 
must obtain a station license before it can be operated if 
the signals radiated therefrom can be heard in another 
state ; and also if such a station is of sufficient power as 
to cause interference with neighboring licensed stations 
in the receipt of signals from transmitting stations out- 
side the state. These regulations cover the operation of 
radiotelephone stations as well as radiotelegraph sta- ' 
tions. 

Station licenses can be issued only to citizens of the 
United States, its territories and dependencies. 

Transmitting stations must be operated under the su- 
pervision of a person holding an Operator's License and 



180 KADIOTELEPHONY 

the party in whose name the station is licensed is respon- 
sible for its activities. 

The Government licenses granted for amateur stations 
are divided into three classes as follows : 

Special Amateur Stations known as the "Z" class of 
stations are usually permitted to transmit on wave 
lengths up to approximately 375 meters. 

General Amateur Stations which are permitted to use 
a power input of 1 kilowatt and which cannot use a wave 
length in excess of 200 meters. 

Eestricted Amateur Stations are those located within 
five nautical miles of Naval radio stations, and are re- 
stricted to 1-2 kilowatt input. These stations also cannot 
transmit on wave lengths in excess of 200 meters. 

Experimental stations, known as the "X" class, and 
school and university radio stations, known as the "Y" 
class, are usually allowed greater power and also allowed 
the use of longer wave lengths at the discretion of the 
Department of Commerce. 

MUST NOT SEND FAKE CALLS. 

All stations are required to use the minimum amount 
of power necessary to carry on successful communication. 
This means that while an amateur station is permitted 
to use, when the circumstances require, an input of 1 kilo- 
watt, this input should be reduced or other means pro- 
vided for lowering the antenna energy when communi- 
cating with near-by stations in which case full power is 
not required. 

Malicious or wilful interference on the part of any 
radio station, or the transmission of any false or fraudu- 
lent distress signal or call is prohibited. Severe penal- 
ties are provided for violation of these provisions. 

Special amateur stations may be licensed at the discre- 



MIRACLE OF THE AGE 181 

tion of the Secretary of Commerce to use a longer wave 
length and higher power than general amateur stations. 
' Applicants for special amateur station licenses must have 
had two years ' experience in actual radio communication. 
A special license will then be granted by the Secretary of 
Commerce only if some substantial benefit to the science 
of radio communication or to commerce seems probable. 
Special amateur station licenses are not issued where in- 
dividual amusement is the chief reason for which the 
application is made. Special amateur stations located on 
or near the seacoast must be operated by a person hold- 
ing a commercial license. Amateur station licenses are 
issued to clubs if they are incorporated, or if any mem- 
ber holding an amateur operator 's license will accept the 
responsibility for the operation of the apparatus. 

Applications for operator's and station licenses of all 
classes should be addressed to the Radio Inspector of the 
district in which the applicant or station is located. Radio 
Inspectors' offices are located at the following places: 

First District Boston, Mass. 

Second District New York City 

Third District Baltimore, Md. 

Fourth District Norfolk, Va. 

Fifth District New Orleans, La. 

Sixth District San Francisco, Cal. 

Seventh District Seattle, Wash. 

Eighth District Detroit, Mich. 

Ninth District Chicago, 111. 

Xo license is required for the operation of a receiving 
station, but all persons are required by law to maintain 
secrecy in regard to any messages which may be over- 
heard. 

There is no fee or charge for either an operator's 
license or a station license. 



CHAPTEE XIX. 

Radio as an Agent of Mercy and the Protector of Man — 
Heroes of the Wireless — The Titanic and Carpathian. 

THE sensationally rapid development of radioteleph- 
ony has naturally been followed by many weird 
theories, and much speculation as to its future avail- 
ability to man and hundreds of prophecies have been 
made as to things that would be accomplished through or 
by it within a few years. 

Because of the simplicity with which a message can be 
broadcast to thousands of places with one operation the 
possibilities of radiotelephony as an aid to state and 
local governments and the police in running down crimi- 
nals seeking to avoid the consequences of their acts was 
quickly seen and sending and receiving sets were early 
installed in the police headquarters or municipal build- 
ings in a number of cities. 

With the radio, not only could all of the police stations 
in the city at once be notified to be on the lookout for a 
suspect or criminal whom it was desired to arrest, but the 
message would at the same time be received in any adja- 
cent or distant city toward which, the criminal might be 
expected to flee. 

The radio, too, makes it possible for the head of a de- 
partment, if he chooses, to address his entire force of 
officers in all the station houses of a city. All that is 
necessary for this is to have radio receiving sets equipped 
with amplifiers or "loud speaker s" installed in each 
station, so that the officers in the room can hear the mes- 
sage without using the ordinary headpiece designed for 

182 



MIRACLE OF THE AGE 183 

service where the sound is not amplified sufficiently to be 
heard in an open room or chamber. 

But speculations as to the future use of the radio, in 
some form or another, in criminal detection goes much 
further than this. 

It has been suggested by Edouard Belin, of Paris, 
and others that since it is now possible to transmit pic- 
tures by telegraph, a similar picture might be transmitted 
by means of an electric wave passing through the ether 
without wires. 

The method by which it is thought this can be accom- 
plished is through the simple expedient of synchronizing 
the existing machinery at each end of a current that is 
now adapted to the recording of visual impressions. 
Portrait photographs have already been telegraphed 
between New York and Chicago and New York and St. 
Louis and the pictures reproduced in the daily news- 
papers, and it is held that such photographs may ulti- 
mately be sent by wireless. 

SEND FINGER PRINTS BY WIRELESS. 

The system by which this has been accomplished and 
known as the Belin process has been improved to such 
an extent since its original creation as to enable M. Belin 
to transmit over a wire in France a reproduction of 
finger prints made by the Bertillon system for identify- 
ing criminals sought by officials. 

The apparatus has been adopted by the French govern- 
ment and has been installed in some of the frontier cities 
in France. The transmission of the finger prints by tel- 
egraph from Paris to one of these frontier points, per- 
haps a hundred miles distant is said to be accomplished 
in about fifteen minutes. 

The instrument is called a "telestrograph" and works 



184 RADIOTELEPHONY 

on the principle of those originally devised for telepho- 
tographic reproduction. A copper cylinder is operated 
by a clock attachment. There is what is termed as an 
interrupted holding a needle. When the current passes 
through the machine as the cylinder turns around the 
needle lifts every time it meets a line on the picture 
being sent. The circuit is broken by this action and the 
breaks register at the other end of the line and on a re- 
ceiving machine the permit is registered just like it is 
sent. The photograph is finished like an ordinary photo- 
graph from the negative thus produced. The same pro- 
cess is used in producing the lines of the finger print. 

The contention is that the radio can be used to send 
pictures and prints through the medium of this machine, 
and the finger prints of a wanted criminal could be in the 
hands of every police department in the world in short 
time. 

In places where the Belin system has been installed 
both photographs and finger prints of the criminals are 
being telegraphed and every police station is shortly pro- 
vided with the perfect identification marks of the man 
sought. The one serious obstacle to the use of the wire- 
less for this system is that bane of the radio operator's 
existence — the condition known as static. It is a condi- 
tion of the elements that makes it difficult or impossible 
for the operator to work his machine. 

Every amateur operator of a radio knows what is 
meant by static. His machine is working smoothly and 
he is delighted. Suddenly there reaches his ears a 
sputtering and then all is silent. Nature has intervened. 
Experts are working to overcome such difficulties, and 
they will do so but up to this point the radio is unsteady 
and the telegraph wire is dependable, so the latter is best 



MIRACLE OF THE AGE 185 

for photographic reproduction where things must be as 
nearly perfect as possible. 

But there is every reason to believe that the "static" 
which is now such an obstacle may be turned to the ac- 
count of man and prove of inestimable value. Nikola 
Tesla has already lighted electric lamps at a distance of 
several hundred feet by wireless and has expressed his 
belief that power will some day be radiated from a gigan- 
tic station to transmit light and power for commercial 
purposes to distant communities by wireless. 

Since ' ' static ' ' is the natural electric discharges in the 
atmosphere, and they are being picked up by every radio 
operator, it is held that this electric energy which per- 
meates the atmosphere and sends out waves into the 
ether may be purposely taken up by man and literally 
harnessed and put to commercial uses. The flashes of 
lightning are the result of nature's "broadcasting sta- 
tion" transmitting electric energy, and men with vision 
see in the future a world running its factories and light- 
ing its cities with electricity drawn from the atmosphere. 

MAN MAY TALK FROM THE WILDERNESS. 

There is a new phase developing almost daily. One 
of the very late experiments showing the progress and 
possibilities of radio was that in which Mr. H. B. Thayer, 
president of the American Telegraph and Telephone 
Company, conversed from his home in Canaan, Conn., 
to Captain Emd, of the Ocean liner America 360 miles 
at sea, through the medium of the ordinary telephone and 
the radio. The remarkable feature about the demonstra- 
tion was that it was a two-way conversation. That is Cap- 
tain Eind and Mr. Thayer talked just as they would over 
an ordinary telephone, although part of the conversation 
was carried on through the "ether." 

To make such a conversation possible it was neces- 
sary to broadcast Captain Eind's salutation and com- 



186 EADIOTELEPHONY 

ments 120 leagues to the wireless station at Elberon, N. 
J. The radio message was then so modified and rectified 
that the waves became andible over the land wires run- 
ning from Elberon to Mr. Thayer's home. When Mr. 
Thayer replied to Captain Eind his voice was carried 
over the land telephone wires to the wireless transmit- 
ting station at Deal Beach, N. J., from where they were 
broadcasted and received on the America by the com- 
mander. 

On the land there were, as indicated, two stations used 
to make the two-way communication possible. One to 
receive the messages from the ship and to forward them 
by land wire, the other to receive the messages over the 
land wire and relay them by radio to the vessel, but on 
shipboard Captain Eind carried on the conversation by 
the use of duplex devices familiar in telegraphy and 
radio work. He was thus able to carry on the conversa- 
tion and hear the broad cast messages from Mr. Thayer 
at one and the same time. 

Some idea of how this might be accomplished may be 
gained by the amateur who has seen the operator of a 
radio receiving set place the radio receiving phone to the 
transmitter of an ordinary telephone so that the person 
at the other end of the telephone line could hear the 
music. The significance of the experiment is tremendous 
when considered with relation to men compelled to enter 
isolated parts of the world where there are incomplete 
lines of communication. It shows how radio can be 
linked up with existing lines, and messages relayed 
around the globe. 

The vast forests and the wildernesses which man could 
not enter without being cut off from the civilized world 
may be invaded with the consciousness that calls for aid 
may be sent out from the most desolate, uninhabited 
places. The tragedies of the north and south poles will 



MIKACLE OF THE AGE 187 

be things of the past and the fastness of the jungle will be 
robbed of its terrors for the explorer because of radio. 

Livingstone, the African explorer, could have told the 
world of his whereabouts when lost in the jungle had the 
radio been available to him, and Peary at the north pole 
could have summoned his relief ship and avoided much 
hardship. Eobert Scott, the English explorer, whose 
frozen body with those of four of his officers was found 
in the ice of the Antarctic region after he had reached the 
south pole, might have been saved had the radio been in 
existence. The party was lost because of their inability 
to communicate with the outside world or the main por- 
tion of their own party. 

With the radio the pioneer hunter or explorer may now 
keep in touch with his fellowmen a thousand miles or 
more away and summon assistance by airplane. The 
missionary in an isolated and lonely territory may have a 
radiophone which will serve to entertain him in his cut- 
off portion of the world, even if the device were not used 
to protect or save him. 

RADIO MIGHT SAVE EXPLORERS. 

But far and beyond even this the radio and the airplane 
together will make it possible to chart and map parts of 
the great world as yet uncharted. Not much of the big 
sphere remains untouched by modern man, but many 
places have not been charted because the knowledge of 
precise time is essential to the work. Where wire com- 
munication is had with Greenwich, the information ob- 
tained from that centre is used to determine both time 
and space, but Greenwich could not heretofore be reached 
from the north pole or the great frozen zones at the ends 
of the earth. 

The wireless will make it possible for the geographer 
to obtain the time and necessary information from 



188 KADIOTELEPHONY 

Greenwich and make exact scientific reports that will 
eliminate all question of doubt as to the precise location 
of any portion of the earth he may have reached. 

Pioneers in the great gold or oil fields in South America 
or Africa, or any undeveloped portion of the world can 
use the wireless in some degree to communicate with out- 
posts, now days away from the seat of their operations. 
This is not mere theory and hope. Already mountain 
climbers are using wireless to report their whereabouts 
to the headquarters from which they operate and stories 
of what the radio has done at sea are legion. 

AN AID TO PIONEERS. 

It was the wireless telegraph which called the Carpa- 
thian to rescue the passengers from the great steamship 
Titanic when it struck an iceberg and sunk off the coast 
of Nova Scotia in 1912, and now the "loop" of the radio 
has been turned to account as a direction finder, through 
the agency of which vessels may be brought into danger- 
ous harbors at night and safely anchored without the aid 
of a pilot. 

And if speculations may enter into our calculations 
they may carry us to other realms and the effort to com- 
municate with Mars, which has been going on for years, 
may be solved by the radio. There are those too, who 
accept the proof of wireless communication as evidence 
that the contentions of the spiritualists are correct and 
that it is possible to communicate with the spirits beyond 
the Styx — the other world — and that a new science is 
being developed which will open wide to the world a book 
that has for centuries been a closed volume. 



CHAPTER XX 

Broadcasting — How It Affected the Development of 

Eadio — Big Electrical Company Pioneers in the Field — 

Colleges — Telephone Companies and Amateurs. 

WHATEVER of interest there may be in radio- 
telephony for the man of science or invention, the 
mechanic, the one who finds delight in delving 
into the mysterious and the unknown, or the person who 
sees in it an opportunity for commercial gain, its sudden 
and overwhelming popularity had its inception in broad- 
casting. 

It is true that the discovery of the electron tube and 
development of the mechanical apparatus used in radio- 
telephony to a point of comparative efficiency have to be 
effected before it could ever become popular or of wide 
practical use, but wireless telephony has been in existence 
for a dozen years. Why did it suddenly spring into popu- 
larity! 

The answer is broadcasting. For half a score of years 
government experts, radio engineers, the geniuses of the 
great telegraph and telephone companies and men of 
science and vision in the great electrical laboratories, plus 
a small group of amateurs, made up the little army that 
found interest in the idea of talking through space with- 
out wires to carry the sound. 

The public heard about the marvelous experiments that 
were being made and how some radio engineer talked 
through space — perhaps 50 or 100 miles — and that was 
all. Radio was viewed as a thing of science, and not a 
thing in which the public could find interest. 

The idea appealed to the imagination, and there were 

189 



190 EADIOTELEPHONY 

some who capitalized this and used their knowledge of 
the progress being made by experimenters as the basis of 
stock promotion schemes in which many persons lost 
money, but in general radio was regarded as a seven days 
wonder. 

Then came the now famous vacuum tube with its un- 
limited capabilities. Not only could it be used as a recti- 
fier or regenerator, to transform alternating currents into 
a direct current, but as a generator of alternating cur- 
rents for radio, a device for charging storage batteries 
from an alternating current, an amplifier of a weak cur- 
rent of electricity or a modulator of a strong current, as 
well as a relay repeater for regular telephone use — ap- 
plied in long-distance telephoning so that the voice cur- 
rents growing weaker after traveling hundreds of miles 
over the wires are given new impetus and travel on their 
way. 

TELEPHONES HELPED DEVELOPMENT. 

Telephone engineers saw the possibilities of the little 
device and they took it for their own. They used it for 
transcontinental service and to multiply the capacity of 
their wires, for the electron tube, incidentally made it pos- 
sible to send a large number of messages over a single 
wire at the same time. 

It was the engineers of the great telephone and tele- 
graph companies that telephoned from Arlington, Va., to 
the Eiffel Tower in Paris, a distance of more than 3,000 
miles back in 1915, and it was the electron tube — or rather 
a battery of them (for several hundred of them were used) 
which made this feat possible. 

Then came broadcasting. The United States Navy first 
made successful attempts in this direction as indicated 
elsewhere in this volume, but it was the Westinghouse 



MIRACLE OF THE AGE 191 

Company that saw in this phase of the art the possibili- 
ties which have since been, and are being realized. 

This great commercial company first broadcast from 
its Pittsburgh experimental station in the latter part of 
1919 or early part of 1920. They first sent ont music 
from phonograph records. Amateurs were at work with 
radio outfits in all parts of the country, and after several 
experiments the company began getting notes from per- 
sons in various sections of the country telling them that 
the music had been picked-up — heard. 

The development was rapid. The operators learned 
what type of music reproduced or carried best on the 
waves and how to talk into the transmitter to get accepta- 
ble results. When desirable things were sought to fill up 
the, at that time, hit-or-miss programs, it was suggested 
that a church service be sent out. 

CHURCH SERVICES POPULAR. 

Early in January, 1921, the first church service in the 
history of the world was broadcast from the Westing- 
house wireless station in Pittsburgh. It was the service 
of the Calvary Episcopal Church. In order to broadcast 
the service wires were connected with the church and 
microphones were installed within the church to catch the 
voice of the rector, the choir and even the chimes. 

This portion of the broadcasting program struck the 
popular fancy and many letters of appreciation were re- 
ceived and the service was made a regular feature of the 
broadcasting. Incidentally out of this experiment grew 
another. One of the Presbyterian churches was without 
a pastor, and someone suggested that the service being 
sent out by the Westinghouse Company be received in the, 
church. A receiving set was installed in the church with- 
a phonograph horn attachment — or what is now com- 



192 EADIOTELEPHONY 

monly referred to as a loud speaker and the members of 
the Presbyterian congregation assembled to hear an 
Episcopal service by radiophone. 

Singers and speakers were substituted for phonograph 
music. Then came the broadcasting of news items, 
weather forecasts, crop reports, grand opera, concerts, 
bedtime stories and educational talks. The demand for 
radio sets outgrew all anticipations. Other broadcasting 
stations were established at Chicago and Newark and also 
at Springfield, Mass. 

The American Eadio and Eesearch Corporation, with 
an experimental station at Medford Hillside, Mass., and 
the General Electric Company of Schenectady opened 
stations and the popularity of the radio was more than 
assured. The demand for sets became a craze. The com- 
mercial possibilities were recognized as were the scien- 
tific, educational and publicity values. 

MILLIONS HEAR CONCERTS. 

Broadcasting stations were established by colleges and 
by municipalities and the department stores came into the 
field. The average radio receiving set, made by amateurs, 
or sold within range of the purse of the youth of the land, 
would not pick-up messages beyond a range of twenty-five 
or fifty miles, and the establishment of transmission, or 
broadcasting stations by the department stores and those 
interested in the sale of radio sets opened a field of possi- 
bilities for the person who did not wish to invest a large 
sum of money in a new plaything, no matter how inter- 
esting it might be. The local broadcasting stations made 
it possible for millions to hear concerts, music, lectures, 
talks on popular and current topics and receive the news 
of the day, as well as information about radio. 

The broadcasting station of a department store in a 
city like Philadelphia, New York or Chicago could be 



MIRACLE OF THE AGE 193 

picked up by boys and girls with receiving sets costing 
probably from $15 to $25, or with sets made at home that 
involved only a few dollars and a little ingenuity. 

Every day brought forth something new. The Bell 
Telephone Company saw in the broadcasting a possibility 
not even yet fully capitalized in the commercial field. 
They established a broadcasting station in New York, not 
for the purpose of sending out regularly prepared pro- 
grams of music, lectures and whatever might be popular, 
but for the purpose of leasing the service or the broad- 
casting privilege to those who might wish to address the 
millions who reside within range of the electric waves the 
station could transmit. 

ITS USE IN POLITICS. 

If a politician had a message he wished to deliver to the 
millions within the territory, he could by paying for the 
privilege address the thousands of people in the homes 
and institutions where radio receiving sets were installed. 
Newspapers could secure the services of this broadcasting 
station to send out election returns, or to announce the re- 
sult of some great boxing match. 

How far this sort of thing can go is still a matter of 
conjecture because the situation can only be met as it 
develops, but the government, which has fostered radio- 
telephony in America, quickly saw the evils that might 
result from permitting everyone to operate a broadcast- 
ing station and the restrictions that held during the war, 
of licensing all broadcasting stations and grading them, 
was adhered to, and in addition the business people were 
given to understand that it was desired they not use the 
broadcasting privilege to force owners of radio receiving 
sets to listen to purely advertising talks — statements re- 
garding the prices of silks, or shoes, or hats or what not. 



194 EADIOTELEPHONY 

Fortunately the radio was largely a one-sided affair 
with the public taking no part in the broadcasting, be- 
cause they could not be equipped to send out messages, 
and listeners-in were spared the necessity of listening to 
the ramblings of some amateur more interested in his 
own plaything than in providing amusement for thou- 
sands around him. 

The natural restrictions placed upon broadcasting is 
primarily one of cost because it requires some sort of an 
efficient and powerful alternating current generator for 
transmission, and the installation of this adds largely to 
the cost of the fun. In addition the operator is compelled 
to pass an examination before the government will issue 
a license for broadcasting. 

In this connection it should be remembered when the 
, call letters of a broadcasting station are heard or seen in 
print, that the letters are assigned to these stations by the 
government so that their calls can be identified and any 
message that comes from them can be checked up should 
they transmit anything of which the people complain or to 
which the government might object. 

A WONDERFUL DEVELOPMENT. 

Throughout the country there are amateurs who are 
among the leaders in radio work, and they have developed 
some interesting things. One of these in Philadelphia 
during the latter part of April, announced that he would 
permit listeners-in to hear their own voices if they would 
phone to him when he was broadcasting. He had the re- 
ceiver of his regular telephone fixed close to the trans- 
mitter of his radio set. Some of his listeners-in took him 
at his word and called him on the phone and all of those 
who were receiving his waves heard the telephone calls 
as they were made including the persons who made them. 



MIRACLE OF THE AGE 195 

The idea took and within a short time he was compelled 
to ask the listeners-in to desist from calling him. The 
telephone lines were congested and the operators could 
look after no other business on the trunks. The telephone 
company asked him to stop the proceeding declaring that 
they had several hundred calls on the phone waiting for 
him. 

There is not, however, in broadcasting, the element of 
interest that is found in receiving, for there is something 
almost uncanny about talking into a machine which does 
not give you any applause, request an encore or tell you 
whether they even heard you or not. Of course there 
could be a receiving apparatus to bring your own message 
back to you, but you have no way of knowing what the 
other fellow thinks of your solo or talk. 

Those who have for the first time sung or talked into 
the radiophone say that the impression is uncanny. No 
sea of faces to look down upon, no familiar stage, none of 
the things which one is accustomed to see and to feel are 
about. A talk with no one to give back a hint that you are 
understood, no smiles, no frowns, no suggestion of ap- 
proval or disapproval. Your speech begins in a silent 
room in which a large disc hangs before you. Some radio 
apparatus is near at hand and perhaps a director or an- 
nouncer stands by. You are alone and you might, so far 
as your consciousness of results are concerned, be de- 
claiming in some sound proof studio of practice. Because 
this fact is recognized, a group of minstrels singing in the 
Pittsburgh station paused when their melody had passed 
out on the waves, and announced that because they knew 
the audience could not applaud they would make up for 
the deficiency in their program by encoring themselves. 
Their handclaxjping was heard by thousands of listeners- 
in and then the minstrels gave their encore. 



CHAPTER XXL 

The Theory of Eadio — Basic Principles Explained with 

Diagrams — Transmitter — Aerial — Tuning — Receiving 

Set — Detector — Vacuum Tube. 

IT has repeatedly been stated and with distinct purpose 
in previous pages that wireless telegraphy and teleph- 
ony consists of communication carried on through the 
medium of the ether with electricity as the agent of trans- 
mission. 

The process of communications consists of setting in 
motion a train of electric waves in one place and detecting 
them at another. The point at which the waves are 
started is called the "transmission station' ' and the point 
at which they are detected the ' i receiving station. ' ' The 
apparatus used to generate and send forth the electric 
waves is the "transmitter" and that at the receiving end 
the ' ' receiver. ' ' 

The train of waves set up in the transmission station 
travel in the same fashion as water waves travel from a 
spot where a stone or heavy object is thrown into a pool 
of water. It is not possible, therefore, to direct (except 
in a general way) the waves toward any receiving station. 
All receiving stations, consequently, will detect the waves 
from all transmitting stations within the range of sensi- 
tivity of their apparatus. It is possible, therefore, to set 
up a receiving station and detect radiotelegraph and tele- 
phone signals from all over the globe, the only limit on 
the distance from which they may be received being the 
sensitivity of the receiving apparatus. 

The transmitter of the radio set creates the disturbance 

196 



MIRACLE OF THE AGE 197 

in the ether setting up the train of waves. In order to 
fully understand the action it is necessary to digress a lit- 
tle and consider the two kinds of electrical currents avail- 
able. Electrical current exists in two general forms: 
direct current, which flows continually in the same direct 
tion in the wire and alternating current which flows first 
in one direction and then in another, changing the direc- 
tion of the flow so many times per second. Each change 
in direction in an alterating current is known as a cycle 
and the number of changes or cycles per second is known 
as the frequency. A current which changes sixty times a 
second is called a sixty cycle current and the frequency is 
stated to be sixty. 

THE TRANSMITTER. 

Investigation has shown that the direct current makes 
no waves, and only alternating currents create a disturb- 
ance in the ether; consequently, this is the current used 
in radio transmitting sets. Careful experiment has 
proved that all electric waves travel with the same ve- 
locity through space, the velocity being 186,000 miles or 
300,000,000 meters per second. If an alternating current 
is created of 50,000 cycles per second and the circuits so 
arranged that the current causes a disturbance in the 
ether of that frequency, each cycle or individual disturb- 
ance will travel through space at the rate of 300,000,000 
meters per second. As there are 50,000 disturbances or 
cycles per second, the first disturbance will be 300,000,000 
meters away by the time the last disturbance is complete. 
We have in the 300,000,000 meters, therefore, 50,000 sepa- 
rate disturbances separated by the distance that 50,000 
divided into 300,000,000 will give, which is 6,000 meters. 
It is the actual distance in meters between the separate 
disturbances and is known as the "wave length/ ' 

All radio transmitters consist of a combination of cir- 



198 EADIOTELEPHONY 

cuits and apparatus capable of creating alternating cur- 
rents of high frequency. This frequency is impressed on 
the ether and the disturbance created; common practice 
designates the disturbance not by the number per second 
but by the actual length of the waves created, calling each 
disturbance, or the frequency of the disturbance, the 
1 ' wave length ' ' of the transmitter. Amateur stations are 
limited to wave lengths of 200 meters. Their transmitting 
apparatus must therefore be capable of producing alter- 
nating currents of 200 divided into 300,000,000 or 1,500,- 
000 cycles per second. 

There are numerous ways of producing alternating cur- 
rents of this frequency and a complete consideration is 
not possible or necessary to this explanation. Perhaps 
the simplest one to consider is the one first used in the 
art: 






F 



if-^rt 



o 



i 



■9 



B C 



<Z 



J=— o 



G — 



Fig. 1. 



The diagram in Fig. 1 shows the elementary radiotele- 
graph transmitter. The wires * ' D ' ' ' ' D ' ' lead to a source 
of high voltage such as a spark coil or transformer oper- 
ating on alternating current used for lighting. The trans- 
former charges the condenser "C," which is connected to 
the coil "B" and the gap "S," to a voltage sufficiently 
high to jump between the two terminals. On the passage 
of the spark there is an interchange of energy between 



MIRACLE OF THE AGE 199 

the coil ' ' B ' ' and the condenser U C," the exchange taking 
place at a frequency determined by the size of "B M and 
"C." By properly regulating the sizes, the frequency 
(and hence the wave length) may be made as high or as 
low as desired. A circuit of this type is called an ' l oscil- 
lating' ' circuit, since the energy present "oscillates" be- 
tween the coil and the condenser. It is universally used 
in one form or another in radio transmitting and receiv- 
ing sets. The coil "F" placed in close proximity to the 
coil "B" will have alternating currents induced in it when 
properly adjusted and will convey them to the "aerial" 
which will create the disturbance desired in the ether. 
This is the simplest form of circuit. It is still quite gen- 
erally used by the beginner, and, with modifications, by 
practically all the vessels equipped with radio sets. The 
most modern and best method of creating the high fre- 
quency necessary for radio work employs vacuum tubes. 
This method will be considered later. 

THE AERIAL. 

Although any alternating current will cause a disturb- 
ance in the ether regardless of the size or shape of the 
circuit, in order to create the maximum disturbances pos- 
sible with the power available, it is necessary to erect an 
1 ' aerial. ' ' 

The aerial or antenna consisting of wires stretched 
above the surrounding objects and connected to the radio 
set is used for both transmitting and receiving, a switch 
or other transfer means being used to connect it to one or 
the other according as the station is sending or receiving 
messages. 

The wires used in aerials is either bare copper, phos- 
phor-bronze or copper clad steel. The ends of the wires 
are insulated with special insulators and the wire lead 



200 



BADIOTELEPHONY 



into the house through an insulating tube known as a 
' ' bulkhead ' ' insulator. 

Where only reception is desired the aerial may be 
strung inside the house. It should be at least thirty-five 
feet long and consist of four wires. Surprising results 
may be obtained by an aerial of this kind and its con- 
venience makes it popular with amateurs living in apart- 
ment houses. 

Equally important is the ground connection. This is 
generally made to the water pipe system in a house. It 
may be further improved by burying a series of wires in 
the ground under the antenna. One form is known as the 
"counterpoise" which is a replica of the antenna but 
placed beneath the ground. A common form of aerial 
or antenna is shown in Figure 2. 



Mi 



JW^J 




Fig. 2. 

TUNING. 
This operation has always been a puzzling one to be- 
ginners. It is, however, very simple. Under the preced- 
ing section dealing with transmitting sets the relation of 
the "wave length" and the "frequency" of the alternat- 
ing current was explained. It was stated that by varying 
the size of the coil "B" and the condenser "C" the fre- 



MIRACLE OF THE AGE 



201 



quency of exchange of electrical energy between them, 
and hence the wave length, could be regulated. Consider 
the circuit shown in Figure 3. 

Assume that the wires * * KK ' ' are connected to a source 
of electrical energy the frequency of which is varied by 
changing "B" and "C." Vary "©" leaving "B" fixed 
until a frequency of 1,000.000 cycles or a wave length of 




G - 



Ammeter 



Fig. 3. 



300 meters is obtained; now vary "C" and "D" and it 
will be found that for a certain point, and that point only, 
that ammeter measuring the current gives a reading. 
This process is known as tuning and the point at which 
the ammeter gives a reading is known as the "resonant" 
point. 

All transmitting and receiving sets operate in the above 
manner, the difference in the sets being due to the methods 
used in varying "B" and "C," and "C" and "D". The 
operation of "tuning" just explained applies to transmit- 
ting sets; the action must be reserved for receiving. 



202 



EADIOTELEPHONY 



Condenser "C" and coil "D" are first adjusted; and 
then "B" and "C" varied. High frequency alternating 
current will be obtained from the wires "KK" but the 
voltage and current will be in the order of millionths of a 
volt or ampere. A meter cannot be used and a device 
known as a "detector" is employed which, with telephone 
receivers, makes the currents audible. 

RECEIVING SET. 

From what has already been stated the reader should 
be able to conceive some idea of what a receiving set 
ought to consist. Eeduced to essentials the diagram of 
connection is shown below in Fig. 4. 




Detector 



Telephones 



Fig. 4. 



It should be noted that the scheme of connection is al- 
most similar to the transmitting set with the one excep- 
tion that a detector and telephones have been added. 

The operation has already been explained ; the various 
"wave lengths" are obtained by varying the frequency of 
the circuits and the alternating current obtained from the 
distant transmitting station is impressed on the "de- 
tector. " 



MIRACLE OF THE AGE 203 

The wave motions are felt in the antenna "A" and 
enter through the coils "D" and "B," usually combined 
in a loose coupler, an instrument constructed of two coils 
of wire and so arranged as to permit of ready variation of 
"D" and "B" and to permit of variation of one coil with 




LOOSE COUPLER. 



reference to the other. The coupler in its commonest 
form consists of one coil wound on a fibre or other tube 
probably three inches in diameter, with a secondary coil 
wound on a similar tube of smaller size, so that the sec- 
ondary coil may slide within the first. The condenser 
" C ' ' is an instrument that stores up electric energy and 
discharges the full charge at once and under high tension. 
It usually is made of alternate layers of a conductor and 
nonconductor so that the layers or plates may be turned 
to have a greater or lesser amount of surface adjacent to 
each other — the plates do not come in actual contact. 
Condensers collect the energy and are also used to put 
the circuits into resonance for tuning. 

THE DETECTOR. 

This is one of the most important parts of the receiving 
set. From what has been said of wave length and fre- 
quency the reader has probably gathered that the frequen- 
cies employed in radio are extremely high. Frequencies 
lower than 20,000 are seldom used and if they were im- 
pressed on the telephone receivers, the note, even if the 



204 EADIOTELEPHONY 

receivers would respond, would be inaudible, since the ear 
will not record frequencies much above 15,000 cycles. 
The problem now is to reduce the frequency used in radio 
to one audible in the telephone receivers. This is done in 
the detector. This instrument groups together a number 
of the cycles of high frequency current and delivers them 
as one cycle of low frequency audible in the telephone re- 
ceiver. 

The detector may be of any one of several shapes and 
types, but the commonest forms is the crystal of galena 




Fig. 5. 

(sulphide of lead) and a contact point of fine wire. One 
type is shown in Figure 5. 

When the wire is lightly brought into contact with the 
surface of the galena the signal received by the antennae 
is changed from alternating current to direct current in a 
series of pulsations that act on the telephone receiver as a 
low frequency alternating current. This low frequency 
current corresponds exactly to the impulses sent out by 
the transmitting station and the audible signals are copied 
as the message. They may, of course, be in code or radio- 
telephone conversations. 

The foregoing outlines the operation of a simple radio 
station. It is given with the idea of fixing the funda- 
mental principles in the mind of the reader rather than of 



MIKACLE OF THE AGE 



205 



KEY TO SYMBOLS OF APPARATUS 




NO CONNECTION 
COUPLED COl IN- 
VARIABLE COUPLING 
DETECTOR 
GALVANOMETE 

GAP. PLAIN — • #_ 

GAP. QUENCHED ||||||||L_ 

GROUND -^j=F 

'nouctor ORFttRRl. 



mD^o^^ " 7 ^ 



INDUCTO 
KEY. 



RESISTOR 



VARIABLE 
RESISTOR 




LOOP 



These symbols are used in diagrams to indicate the various parts 
of radio apparatus. 



206 



EADIOTELEPHONY 



showing the actual construction and operation of the sta- 
tion. 

All radio sets are based upon the plans just given and 
iheir efficiency is merely increased by the additions of re- 
finements in the way of amplifiers, rectifiers, condensers, 
form of antenna, telephone head sets and loud speakers 
which have been developed. 



Connections' 
to Filament 





Plate 



Filament'' \6rid 



ToPkte 
^ToGrid 

Fig. 6. 



The most important of these is the vacuum or electron 
tube, which involves but one principle of construction 
though made in variable forms and degrees of efficiency 
control and power. It has previously been described but 
the diagram (Figure 6) will make clear the general rela- 
tion of the filament, the grid and plate. The illustration 
at the right in Figure 6 is a large reproduction of the 
"symbol" used in working diagrams to denote the elec- 
tron tube. It plainly shows the relation of posts. 



CHAPTER XXII 

Hook-ups an Interesting Study — Same Principles In- 
volved in All — 'Amplification and Refinements. 

THROUGHOUT the preceding pages radio has been 
discussed mainly with relation to its rapid develop- 
ment and the reason for its remarkable popularity. 
For those who are more interested in radio from a prac- 
tical standpoint a summary of facts and some simple 
working analyses will be taken up. 

In the chapter just ended a few diagrams showing the 
basic principles of a radio hook-up have been given and it 
is well to repeat that in all radio work diagrams are used 
to show systems of circuit connection, just as blue prints 
are used in all working plans in the industrial or engineer- 
ing fields. Instead of drawing pictures of the various 
parts of a radio set, the relative positions of such parts 
are indicated in the circuit by symbols, of which the prin- 
cipal ones are shown in the chart at the back of this 
volume. 

There are hundreds of combinations used in connecting 
up circuits — making " hook-ups" — and nearly every ex- 
perimenter will from time to time change his method of 
making connections to find what he believes will prove a 
more efficient system. The fact that a slight change will 
frequently make a big improvement in the efficiency of a 
set is one of the things that makes radio hold particular 
interest for the youth or man who is mechanically or 
scientifically inclined. 

It is not necessary for one to know anything about elec- 
tricity or the scientific side of radio to be able to operate 
an ordinary receiving set, yet nearly every person who 

207 



208 RADIOTELEPHONY 

starts to work in radio ends by delving to some extent 
into the "whys and wherefores" and becomes an experi- 
menter. He is not satisfied to turn a knob or adjust a 
tuning coil and take what he receives. He wants to know 
more so that he can improve his apparatus and get better 
results. There follows in logical order a study of hook- 
ups, the purchase of additional standard parts, or the 
making of substitutes at home, and the effort to properly 
incorporate them in a circuit. 

Anyone reaching this stage must understand some of 
the principles and practices involved in the building up of 
receiving sets. To begin with it should be remembered 
that the aerial in every case forms one end of a circuit 
and the ground the other. The waves are intercepted by 
the antenna or aerial and pass down the lead-in wire to 
the receiving set. Here they first strike the tuner. This 
is a coil of some form which by adjustment permits the 
waves to be received clear and strong. 

THREE FORMS OF CIRCUIT. 

After the waves are "tuned-in" their presence is de- 
tected. The now famous vacuum tube or a crystal de- 
tector is used for this purpose. The tube or crystal, as 
the case may be, is adjusted so that the waves are de- 
tected in their passage from the aerial through the tuner 
and thence to the ground. What actually happens is that 
the detector rectifies the rapid wave vibrations or mo- 
tions and slows them down to a point where they will 
affect the diaphragm of a telephone receiver and they 
become audible. 

So far all seems simple, but in coupling up circuits it 
must be remembered that there are three basic forms of 
coupling: i.e. "direct," "inductive" and "capacity." 
There are in these couplings primary and secondary cir- 



MIBACLE OF THE AGE 



209 



cuits. The primary circuit is that which forms the natu- 
ral wire path from the antenna to the ground. It may 
have incorporated in it coils, condensers or other bits of 
apparatus, but there is a direct path along which the waves 




EXAMPLE OF DIRECT COUPLING. 



or current would naturally travel to the ground. The sec- 
ondary circuit is that by which the waves or current are 
deployed or diverted from the primary so that they travel 
around the secondary and back again to the main circuit, 
and thence over their natural course to the ground. In 




EXAMPLE OF INDUCTIVE COUPLING. 



direct connection the secondary circuit is tied into the 
primary forming two junctions with the primary — one 
where it begins and the other where it ends. In an induc- 
tive coupling the primary circuit is physically undis- 
14 



210 



RADIOTELEPHONY 



turbed. The secondary circuit is arranged in proximity 
to the primary in such a manner that the current or waves 
are carried through it by inductance and not because of 
direct contact. Induction coils arranged side by side — 
one in the primary circuit, the other in the secondary — 
make such a hook-up operative. 

In a capacity coupling there are really two segments or 
half circuits with a condenser incorporated in what would 
logically be the direct or primary to serve as the coupling 
element. The diagrams herewith show the principles in- 
volved. 




EXAMPLE OF CAPACITY COUPLING. 



The simplest circuit of any considerable effectiveness is 
one which consists of the aerial, single or double slide 
tuning coil, crystal detector, condenser and head tele- 
phone receivers. It has been noted before, but is worth 
repeating that such a set cannot be used with any marked 
degree of success for receiving beyond 20 or 25 miles, and 
the amateur who anticipates hearing concerts or ad- 
dresses sent out from stations at a much greater distance 
will be disappointed except under unusual conditions. 
Nor can a loud talker be used on such a set with any de- 
gree of satisfaction. The element lacking for this is some 
system of amplifying the waves to make them more pow- 






MIRACLE OF THE AGE 



211 



erful and pronounced when they reach the receiving 
phones. The diagram shows such a circuit. 

Almost every article written on the principles of radio 
describe such a set as that referred to above though some 
of them omit the condenser. In such sets however, the 
antenna and the earth beneath it form two opposing ele- 
ments of a condenser, having what is technically termed 





CIRCUIT OF EADIO RECEIVING SET WITH DOUBLE SLIDE TUNING COIL, 
CRYSTAL DETECTOR AND SIMPLE CONDENSER. 

an air dielectric between, but the set without the con- 
denser is less efficient. 

With the foregoing facts in mind and remembering that 
the waves have been led into the tuning coil it is worth 
while dwelling on what takes place here. Specifically the 
tuning coil has the effect of cutting out all of the waves 
save those desired. There are innumerable appliances or 
devices used for this purpose including the single and 
double slide coils, loose couplers, one of which is illus- 
trated in a preceding chapter; vario-couplers, vario- 
meters and variable condensers made in varied form. 



212 BADIOTELEPHONY 

One of the commonest forms is the double slide tuning 
coil which it may be well to describe because it is a type 
that the experimenter can easily make. It consists of a 
pasteboard, fibre, or wooden tube about 8 inches long by 
3 inches in diameter, wound from end to end — or over 7 
inches of its surface with 24 B & S gauge single cotton or 
silk covered, or enameled copper wire. The wire must be 
wound tightly so that the coils have no side play, and one 
end of the wire is fastened to or imbedded in the tube. 
The wound tube is mounted between two blocks of wood 
about 5 inches square. The most satisfactory way of 
holding the tube in place is to cut holes in the blocks 3 
inches in diameter so that the tube ends may be forced 
tightly into them. The experimenter will now have a 
wire-wound tube with a block on each end. It would be 
well to glue the tube to the blocks and to shellac the entire 
thing, wire and all. 

ATTACHING TUNING COIL SLIDES. 

The next step is to fasten from block to block — one over 
the top and the other across the front — two brass rods. 
These can be secured to the blocks at either end. On each 
rod there should be a snug fitting slide, to the bottom of 
which there must be a contact point that will touch the coil 
on the tube beneath. Such rods and ' ' sliders ' ' may be ob- 
tained from any dealer in radio supplies or they can be 
made. Where the sliders touch the wire as they are 
moved along its surface from end to end the insulation 
should be scraped off so that the slider point makes a per- 
fect contact. 

With the tuner coil in this shape it is next necessary to 
attach binding posts for the circuit connections. Two 
binding posts must be fastened to the block at the end 
where the wire coil is attached to the cardboard tube. 



MIRACLE OF THE AGE 



213 



One of these posts, preferably the one at the front is to be 
connected to, or with the lead-in wire from the aerial. It 
must also be connected to the sliding rod with a piece of 
wire. The twin binding post at this end is hooked-up or 
connected with the upper sliding rod with a piece of wire 
and is known as the detector connection. 

One single binding post is attached to the opposite end 
of the tube in the square block. To this post is fastened 
the end of the wire coil that was permitted to remain loose 
or extended away from the tube after the winding. In 
hooking-up this binding post is connected with the ground 




imMUtlllll1lllulllllMMIIIIIUIIIIUUIIIIII1lll|\Vl 

uunmimuMMmitumi in mi minim immll 1 

iiiiiiiiiiiMiiiniMniiin'iiiiiH'iiiinfUHiniiiii I 




iiiiuiiijijiijjjiji, !!H!!!!!!!!!!!!!. , !!!J!!!f!J!ft 

Double Slida Timer 

wire in the circuit. The variations required to tune-in on 
waves are secured by operating the sliders. It is obvious 
of course that the waves coming down to the tuner pass 
through the binding post connection to the sliding rod, 
down through the slide contact point and out through the 
end of the coil through the binding post connection at the 
opposite end and oif to the ground, and the manipulation 
of the sliders will regulate and control the waves in their 
passage. A sketch of such a finished tuner is printed 
herewith. 

It is possible for the amateur to make the finer type of 
tuning device, such as the vario-coupler or variometer, 
but great accuracy is necessary and it is much safer to 
purchase them. While on this subject it should be noted 



214 EADIOTELEPHONY 

that the elemental difference between a vario-coupler and 
a variometer is that while both consist of two coils so ar- 
ranged that one turns within the other, in one type the 
two coils are not connected and effect is produced by- 
variation of inductance while in the other device the two 
coils are physically connected. 

It is generally stated that the crystal detector of the 
small radio set is a very simple device but there are a num- 
ber of points not to be forgotten by those attempting to 
make their own detectors. Its construction and function 
may be more readily understood if the direction of the 
current or waves is kept in mind. Assuming for the sake 
of simplicity that the direction of the incoming waves is 
from left to right, the detector is cut into the circuit at 
some point in the line after the tuning coil, or between the 
tuning coil and the head phones. 

A SIMPLE HOMEMADE DETECTOR. 

A familiar form of the crystal detector is illustrated in 
the preceding chapter, but the type that can be made at 
home must be of a character more easily constructed. A 
popular form consists of a block of wood or hard rubber 
about 4 inches long, by two inches wide and perhaps one- 
quarter of an inch thick, to which is attached a binding 
post at either end. In use the left binding post is attached 
to the circuit wire running from the tuner. The binding 
post at the right is connected to a section of wire running 
toward the head phones. Between these two posts on the 
block are mounted at the left a post supporting a sensitive 
contact point or device called a " cat's whisker,' ' and at 
the right of it, and adjacent to the right hand binding 
post is mounted a silicon or galena crystal. A dozen 
methods may be employed to construct the cat's whisker 
and its support, but the simplest is to use a large size 



MIRACLE OF THE AGE 215 

binding post through the wire hole of which at the top is 
fastened a piece of heavy copper wire, that should be bent 
in such shape that it can conveniently be turned on its 
circumference in the binding post hole. To the right end 
of this heavy wire there must be soldered a piece of fine 
wire — a section of fine mandolin wire about one and one- 
half inches long will serve. 

The crystal is mounted on a brass or copper seat of 
some sort attached to the base block. A brass ferrule will 
serve the purpose. The delicate crystal may be held 
firmly by packing it in tin foil. With these mechanical 




A -Home Made Crystal Detector 

parts thus assembled, the post holding the " cat's 
whisker' ' must be connected to the left hand binding post 
with a bit of the regular circuit wire, and the metal base 
support of the crystal must be similarly connected to the 
left binding post. In operation the copper wire with the 
1 ' cat's whisker" must be adjusted so that the fine end of 
the " whisker" comes in contact with the sensitive face of 
the crystal. 

Now when the waves are properly tuned-in and travel 
through the circuit to the detector, the fine cat's whisker 
vibrates, in keeping with the wave motions, but the crystal 
possesses the property of only permitting a certain por- 
tion of the rapid oscillations to pass on through and out 
at the opposite side into the wire connected with the head 
phones. This description may be said to be not wholly 
correct, technically, but it will convey a better idea of the 



216 RADIOTELEPHONY 

mechanical functions of this type of detector than might 
some other description. The accompanying illustration 
will give a clear idea of how such a detector is set up. 

The condenser is the other essential part of such a re- 
ceiving set as is under discussion. This is incorporated 
in the circuit between the detector and the head phones. 
Any number of condensers of simple type have been de- 

Now C ondenser *s&tup 

— — — J N. ft 




Paraffined Paper deparaling 
each piece °f Tin Foil 



1 Finished Condenser 



signed, but the simplest is built up of alternate layers of 
tin foil and paraffined paper cut in strips. There should 
be ten strips of foil about four inches long by three wide, 
arranged as shown in the accompanying diagram. The 
strips of paraffined paper between should be slightly 
wider than the foil sheets. When arranged as shown, the 
paper and foil strips are pressed tightly together with 
pieces of cigar box wood on either side to hold them 
firmly. The diagrams are self explanatory. 



CHAPTER XXIII 

Vacuum Tube Detector Set Next Step of Progress in 
the Building of a Eadio Set — Back to Simple Princi- 
ples of Radio Communication. 

IT is possible to utilize the crystal detector radiotele- 
phone set at greater distance than the amateur is 
frequently given to understand by simply including 
certain cores and tubes, but the next step of progress for 
those who wish to have a reasonably efficient set is to 
make or secure one with a vacuum tube detector. 

The same simple hook-up that is shown in the previous 
chapter for building a detector set with the crystal might 
form the basis for a vacuum tube set with certain modifi- 
cations. It would require the incorporation of a variable 
condenser in the primary circuit as well as one in the sec- 
ondary, together with a grid condenser, an "A" storage 
battery of 4 to 6 volts to furnish current to the filament, 
together with a "B," or dry cell battery of 22% volts con- 
nected with the plate of the tube. A rheostat is necessary 
to control and operate the tube. 

Before going into any further discussion of the prac- 
tical operation of a vacuum tube detector set we shall go 
back to first principles. In the early chapters considera- 
ble attention was given to the rudimentary principles of 
electricity with but little stress upon their application 
and effects in radio operation, particularly with reference 
to telegraphy the thought being that those who found 
sufficient interest in radio to desire to instal a set or ex- 
periment with the waves transmitted through the ether, 
would later be better prepared to absorb what at first 
might seem to be too highly technical. 

217 



218 KADIOTELEPHONY 

In radio as in everything else, we learn by repetition 
and the presentation of a subject from a new angle, and 
there is no better way of making clear the relation of the 
vacuum tube to wave detection than beginning with the 
waves themselves. 

Probably the best informed body of men on the entire 
subject of radio in the country are those identified with 
its use in the army and navy, and the simplest and most 
comprehensive treatise on the elementary principles of 
radiotelegraphy and telephony that has been offered for 
public consideration has been prepared in the office of the 
Chief Signal Officer of the United States Army in "Wash- 
ington. 

It makes clear so many points that are frequently puz- 
zling to even the reasonably well informed that the major 
facts and explanations are incorporated here, beginning 
with the basic statement that " radio communication is 
the art of sending information from one point to a distant 
point by means of free electric waves. The study of radio 
communication, therefore, embraces three separate sub- 
jects: The production of these waves, the waves them- 
selves, and the reception of these waves. 

THE WAVES. 

Every one is familiar with waves, especially with those 
that appear on the surface of water. Let us study these 
water waves. We can represent them by a line as in fig- 
ure 1, where the curving line represents the surface of the 
water with waves on it and the straight line, AB, repre- 
sents the surface of the water when there are no waves. 
The first thing we notice about a wave is its height. The 
stronger the breeze the higher the waves. The correct 
way to measure the height of a wave is to measure from 
the crest of the wave to the surface of the water when it 



MIRACLE OF THE AGE 219 

is smooth. In figure 1 this would be represented by the 
line cd. A better term for this measurement is amplitude 
of the wave. Hereafter we will refer to the amplitude of 
the wave and not to the height. 

If we have been in a boat or in swimming when there 
were waves, we are familiar with the fact that the waves 
have energy. In other words, they have power to move 
objects that are in the water or that they may strike. It 
is seen that the bigger the waves the more energy they 
have. Another way of saying this same thing is to say 
that the energy of a wave increases as its amplitude in- 
creases — a large amplitude gives a large amount of en- 







F1&.1. 








c 
STk — 


7\ 


x*> 


v 


A 


/V\ 


0^ 


^- 


i- 



ergy — a small amplitude gives a small amount of energy. 
In radio we use the energy of the radio wave. 

If we watched water waves we would soon notice that 
besides height, the waves have length also. There would 
be a certain distance from one wave to the next. This 
distance can be measured from the highest part of one 
wave (called the crest) to the highest part of the next 
wave. This distance is the length of the wave. In figure 
1 it is represented by the line ce. Also ff shows the length 
of the wave. The wave length then is the distance from 
any part of one wave to the corresponding part of the next 
wave. 

If we stood on the shore and watched the wave go by we 
would notice that waves, besides having amplitude and 



220 KADIOTELEPHONY 

length, passed us at regular intervals of time. Count the 
number of waves passing per second. You have counted 
the frequency of the waves. Frequency, then, is the num- 
ber of waves passing any point in a second. It is repre- 
sented by the letter "f." 

FREQUENCY AND WAVE LENGTH. 

Suppose now that we wished to know how fast the 
waves are traveling. We could find this out in different 
ways. The easiest way to find it out is to figure it out as 
follows : Suppose each wave is 10 feet long and there was 
one wave passing per second. The wave must be travel- 
ing 10 feet per second, then, in order to get by. If two 
waves per second passed, then the waves must be travel- 
ing 2 X 10 f eet=20 feet per second. If there were 12 waves 
per second and each wave was 10 feet long then the waves 
must be traveling 12X10=120 feet per second, which is 
the rate of travel (velocity) of a wave. Velocity is always 
represented by the letter "v." 

Now we have a very good idea of what water waves are. 
We can sum it up by saying that water waves are recur- 
ring displacements of water, traveling at a definite 
velocity and having definite amplitude, length, and fre- 
quency. These waves carry energy. This is true of water 
waves, and if we say i ' disturbance ' ' instead of ' ' displace- 
ment of water" it would be true of any kind of a wave. 
Waves are recurring disturbance, traveling at a definite 
velocity and having definite amplitude, length, and fre- 
quency. Waves carry energy. 

Each different kind of wave has a definite velocity. 
The velocity of a radio wave is so great that it would go 
around the earth seven times a second if it could keep on 
going. It is 186,000 miles in a second. In radio we do not 
measure distances in miles — we use meters (a meter is a 



MIRACLE OF THE AGE 221 

few inches longer than a yard). The velocity of radio 
waves is 300,000,000 meters per second. 

This velocity is constant, so that in measuring radio 
waves, if we can find either the frequency or the length, 
we know the other. This is true because the velocity is 
always equal to 300,000,000 meters per second. So if we 
know either the frequency or the wave length, the other 
one can always be obtained by dividing the known one into 
300,000,000. 

Examples: (1) What is frequency if the wave length is 
2,000? Frequency is 300,000,000 divided by 2,000=150,- 
000 waves per second. (2) "What is wave length if fre- 
quency is 50,000? 300,000,000-4-50,000=6,000 meters. 
Sometimes one is stated and sometimes the other. Both 
are known when one is, as we have just shown. 

THE ETHER OR MEDIUM. 

In order to have a wave it is evident that there must be 
some material to carry the wave. This thing in which the 
wave travels is called the medium. The medium that car- 
ries water waves is water. Sound is carried by waves in 
air. Air is the medium for sound waves. So in radio 
waves there is a medium which carries them. The me- 
dium is called the ether. Not much is known about the 
ether except that it will carry certain waves very rapidly. 
Besides carrying radio waves, it carries light waves and 
also heat waves. Another fact that is known about the 
ether is the fact that it is everywhere. It is between you 
and every other object. It is between the earth and the 
sun, the moon and the sun, etc. It is in everything, as well 
as in the space outside. It is in the pamphlet you are 
reading — it is in your body. It is everywhere. There is 
no exception to that. You cannot think of a place where 
there is no ether — for there is no such place. 



222 



KADIOTELEPHONY 



The radio waves then are carried by ether. Just what 
are these radio waves? In elementary electricity we 
studied about the magnetic lines of force and showed 
them by iron filings between magnets. A radio wave con- 
sists of these magnetic lines of force and something else. 
That something else is electrostatic lines of force. Elec- 
trostatic line of force are what cause a positively charged 
body to attract a negatively charged body. They go from 
a positive to a negative charge and are quite similar to 
magnetic lines of force. They are caused by a charge of 
electricity and are always present when a body is charged. 



n*.z. 




i 

'i!n M 



i|i»!M;i! 



ill!!!!!!!! 




Amplitude of wave /s represented by the 
density of the lines offeree 



A radio wave then is composed of electromagnetic lines 
of force and electrostatic lines of force. 

A radio wave is represented in figure 2. This figure 
shows a radio wave moving from left to right. The elec- 
trostatic lines of force are represented by lines, the elec- 
tromagnetic line of force represented by little circles at 
the end of the lines. It must be remembered that these 
are lines. They extend at right angles to the electrostatic 
lines of force. They cannot be shown on this diagram as 
lines, so are represented by circles. This wave is usually 
represented by a curved line similar to figure 1. Figure 3 
shows the usual representation. 

Figures 2 and 3 are labeled the same and they show how 
one accurately represents the other, a is the crest of one 



MIRACLE OF THE AGE 223 

wave and a the crest of the next. The distance from a to 
m in figure 3. In figure 2 this amplitude is shown by the 
closeness of one line to another. If the amplitude was 
greater, there would be more lines packed in a given 
space. 

There is one other thing about a wave that we should 
observe. In the water wave we see that part of the water 
in the wave is above the level of the water when it is 
smooth and the other part of the wave is below the level. 
This is true of all kinds of waves — part of the wave dis- 
turbance is on one side of the usual (waveless) condition, 




and the other part of the wave disturbance is on the op- 
posite side of the usual (waveless) condition. This is 
true of the radio waves. Look at figure 2 and note that 
the arrows show that the electrostatic lines of force are 
directed upward in one part of the wave and downward 
in another part. This is also true of the electromagnetic 
lines of force. The open circles represent those that are 
directed toward you; the solid circles represent those 
that are directed away from you. 

It must be clearly understood that this wave travels on- 
ward just as a water wave travels onward. This means 
that any point in the path of the wave is swept by lines of 
force, magnetic and electrostatic, directed in one way and 
an instant later the same point is swept by lines of force 



224 RADIOTELEPHONY 

directed in the opposite way. Between each reversal of 
these lines of force there is a brief instant in which no 
lines of force sweep the point. As we have noted the 
velocity of these waves is 300,000,000 meters per second. 
(They may be of any length ; for example, as short as 50 
meters or as long as 50,000 meters.) 

PRODUCTION OF WAVES. 

We can produce waves in water by various methods. 
But whatever method we use, it is always done by some- 
thing that will cause the surface of the water to move up 
and down. In other words, we must have some contact 
between a moving body and the water. For instance, 
wind will produce waves in water. The moving air comes 
in contact with the water and imparts motion to the water. 
Now, radio waves in ether must be produced in a similar 
way — by something moving capable of affecting the ether. 
The only known thing that is capable of affecting the 
ether is the electron. The only way that electrons can 
produce waves in the ether is by moving rapidly to-and- 
fro. 

Thus to get a radio wave we must have a rapid to-and- 
f ro movement of electrons. These moving electrons pro- 
duce radio waves and the radio waves produced are simi- 
lar in every respect to the motion of the electrons produc- 
ing them. Thus, many electrons moving mean that the 
radio wave has large amplitude (carries much energy). 
The number per second of to-and-fro movements of the 
electrons determines the number per second (frequency) 
of the waves. The wave length is, of course, determined 
by the frequency. The velocity of the wave is always the 
same ; 300,000,000 meters per second. 

Thus in order to produce a radio wave we must pro- 
duce a rapid to-and-fro movement of electrons. In an 



MIRACLE OF THE AGE 225 

alternating current, such as we use for electric lighting, 
the electrons move first in one direction and then in the 
opposite direction ; that is, to-and-f ro. But these changes 
in direction occur only a comparatively few times per 
second — sixty times in most alternating currents. This 
is not rapid enough for the electrons to start a wave, 
containing useful energy, in the ether. To start such a 
wave we must have the alternations ( to-and-f ro move- 
ment) occur 6,000 or more times per second. Alternat- 
ing currents having 6,000 or more alternations per sec- 
ond are said to have radio frequency. The study of the 
production of these high frequency alternating currents 
comprises the greater part of the study of producing 
radio waves. 

OSCILLATIONS DEFINED. 

If we take a weight and hang it on a spiral spring, such 
as is found in ice scales, we can get a vibrating motion 
of the two. By pulling down on the weight and letting go, 
the weight will oscillate (move to-and-f ro) up and down. 
We can change the frequency (number per second) of 
these vibrations by changing the stiffness of the spring 
or by putting on various weights. A study of this motion 
will show that it is the spring that pulls it back to its nor- 
mal position and it is the weight which makes it move 
beyond its normal position. In other words, once we 
have stretched it further than its normal length, the 
spring starts it in motion — and the weight keeps it in 
motion. 

We can get the same effect in another way. Take the 
blade of a hack saw and fasten it in a vise, allowing some 
of it to project. Pull the end to one side and let it go. 
It will vibrate back and forth. By some means fasten a 
weight on the end and watch it vibrate. Notice the change 



226 KADIOTELEPHONY 

in the frequency of vibrations. Change the stiffness of 
the blade (by substituting a different sized blade or by 
shortening or lengthening the blade). Try different 
sized weights fastened to it. You will note that it is the 
combination of weight and stiffness which determines 
the frequency of vibration. Changing either one or 
changing both will change the frequency. You will note, 
too, that once drawn aside (given energy) it is the stiff- 
ness of the blade which starts the motion toward the 
point of rest, and it is the weight which keeps it moving 
beyond the point of rest. 

EFFECTS OF INDUCTANCE. 

Thus you see we can start vibration or oscillation in 
anything if we have these two factors present ; that is, if 
we have something that will start a movement to a point 
of rest (when it has been moved from the point of rest) 
and something that will keep its movement going beyond 
the point of rest. In electricity we have these two factors, 
and it is by using these that we can get radio frequency 
alternations (oscillations) in a circuit. 

Inductance in an electrical circuit has the property of 
resisting any change in the current flowing in that circuit. 
Consider a circuit which has a large self-inductance. 
A current is started in the circuit, and the self -inductance 
of the circuit opposes the building up of that current. 
When the current is flowing if we stop it or diminish it in 
any way, the self -inductance of the circuit opposes the 
stopping or diminishing of the current. In other words, 
inductance opposes any change in the current flowing in 
a circuit. This is exactly the effect of the weight of any 
moving object. An automobile truck is hard to start be- 
cause its weight opposes the starting of it. When the 
truck is in motion and an attempt is made to stop it, it is 



MIRACLE OF THE AGE 



227 



the weight of the truck which opposes the stopping of it. 
Inductance in electricity plays the same role as weight in 
objects. In the same way as the weight made the hack 
saw pass beyond its point of rest, the inductance of a 
circuit will make a current pass beyond its point of rest 
(zero current). 

Capacity in an electric circuit has the property of urg- 
ing a current to the point of rest (zero current) when it 
has flowed beyond the point of rest. Consider a circuit 
containing a condenser (capacity) and a source of elec- 
tromotive force. When the circuit is made the condenser 




gradually charges up from a zero potential to a potential 
equal to that of the charging instrument. When the po- 
tential of the condenser and the charging instrument are 
the same, the current stops flowing because the potential 
of the condenser is urging the current in the opposite di- 
rection to that of the charging instrument. If the source of 
electromotive force is removed and the circuit completed 
the condenser will, because of its potential, cause a cur- 
rent to flow in a direction opposite to that of the first 
current. The condenser potential will act until it has 
been all used up; that is, until the condenser has zero 
potential. Thus capacity plays the same part in an elec- 
tric circuit that a spring (elastic body) does in a material 
body. 



228 



RADIOTELEPHONY 



It is seen, then, that weight and inductance are similar 
and also that elasticity (springiness) and capacity are 
similar. When both inductance and capacity are in a 
circuit they will act exactly as a spring and weight act in 
a material body. That is, if they are furnished with 
electrical energy and then freed from outside influence 
they will oscillate in exactly the same way as the hack- 
saw blade vibrated, due to its stiffness and weight. A 
study of figure 4 shows this similarity. 



HACK-SAW BLADE. 

"Furnish energy by displacing 
the hack-saw blade to position at a. 

"Free the hack-saw blade by re- 
moving the hand. 

"The stiffness (elasticity) of the 
hack-saw blade makes it move from 
its position of displacement, a, to- 
ward the point of rest, r. 



"When the blade reaches the 
point of rest, r, it has its greatest 
speed. 

"Just at the point of rest the 
stiffness of the blade ceases to 
move the blade. 

"The weight of the blade causes 
the blade to move beyond its point 
of rest. 

' ' The further the blade moves be- 
yond its point of rest, the more the 
stiffness of the blade opposes the 
motion. 



"When the blade reaches the fur- 
thest displacement, b, on the other 
side, there is no motion. 



INDUCTANCE AND CAPACITY. 

"Furnish energy by charging the 
condenser so that electrons gather 
on plate of condenser marked a. 

"Free the inductance-capacity 
circuit by removing source of charge. 

"The potential of the condenser 
causes the electrons to move away 
from a to the point of rest. (Point 
of rest is that point where there are 
no excess electrons on either plate of 
condenser.) 

"When the electrons reach their 
point of rest the current has the 
greatest value. 

"Just at the point of rest the ca- 
pacity of the circuit ceases to act. 
(There is no potential.) 

"The inductance of the circuit 
causes the current to keep on mov- 
ing beyond the point of rest. (Zero 
potential.) 

"The longer the current flows 
beyond the point of rest the more 
the capacity of the circuit opposes 
the current. (Because the conden- 
ser is acquiring, by the current flow- 
ing into it, a potential opposing the 
flow of current.) 

"When the electrons have reach- 
ed their furthest displacement 
(charged b to its highest potential) 
there is no current in the circuit. 



MIRACLE OF THE AGE 229 

"The stiffness of the hack-saw "The potential of the condenser 
blade makes it move from this posi- causes the electrons to move away 
tion of displacement toward the from b to the point of rest. This 
point of rest. This movement is oj)- movement, and therefore the cur- 
posit e in direction to the first move- rent, is opposite in direction to the 
ment. first movement. 

"Events repeat themselves as ex- "Events repeat themselves as ex- 
plained, plained. 

"The frequency of vibration of "The frequency of oscillation of 

the blade depends upon the values the current depends upon the values 

of both the weight and elasticity of of both the inductance and capacity 

the blade. of the circuit. 

"Thus it is seen that a current will oscillate in a circuit 
if the circuit has both inductance and capacity. By 
these to-and-fro movements of the electrons, ether 
(radio) waves are started. The length of these radio 
waves, as has been shown, depends upon the number of 
the oscillations in the circuit. Increasing either the 
amount of inductance or capacity in a circuit gives a 
longer wave length. Increasing both gives a longer wave 
length. To increase the wave length, increase either the 
inductance or capacity or both; to decrease the wave 
length, decrease either the inductance or capacity or 
both." 



CHAPTEB XXIV. 

How to Change Inductance and Capacity Energizing an 
Inductance — Capacity Circuit — The Potential — A Sim- 
ple Transmitting System. 

THEEE are various methods of changing the induc- 
tance in a circuit. A straight wire has very little in- 
ductance. Make a coil of the same wire and the in- 
ductance is greatly increased. The coil can be made either 
by winding it smooth over a form, such as a broomstick, 
or by winding it spirally in the same plane. This is the 
way electricians tape comes in the roll. The inductance 
of a coil is changed by changing the number of turns of 
the coil in the circuit. This is the most common way. 

There are various methods of changing the inductance 
in a circuit. A straight wire has very little inductance. 
Make a coil of the same wire and the inductance is greatly 
increased. The coil can be made either by winding it 
smooth over a form, such as a broomstick, or by winding 
it spirally in the same plane. This is the way electrician's 
tape comes in the roll. The inductance of a coil is changed 
by changing the number of turns of the coil in the circuit. 
This is the most common way. 

There are also various methods of changing the ca- 
pacity in a circuit. One method is by changing the num- 
ber of condensers in the circuit. A second method is by 
changing the capacity of a single condenser. This is done 
by having the two sets of plates that make up a condenser 
movable with respect to each other. When every part of 
the plates in one set is opposite to the plates in the other 
the capacity is the greatest. The capacity is made smaller 

230 



MIRACLE OF THE AGE 



231 



by having only a part of each plate in one set opposite to 
the plates in the other. 

The inductance and capacity needed in an oscillating 
circuit is contained in the antenna of a radio transmitting 
set. The antenna of a radio set is that part of the set 
which radiates the energy by setting up the waves in the 
ether as explained above. The wires making up the an- 
tenna give both the capacity and inductance. It, however, 
is very usual to add extra inductance in the shape of a 
coil which may be varied. Capacity also is sometimes 
added by throwing condensers in the aerial circuit. 



Fig. 5. 



T 



Iron Core Choke Coil 



Source of 
high Potential 



* e- 



iSpark Gap 



'."\Condenser ^ 4* 



In order to have radio waves, the electrons must oscil- 
late at the rate of 6,000 or more times a second. That is, 
to start a radio wave there must be an alternating cur- 
rent alternating at the rate of 6,000 or more times per 
second. Up until recent years, there was no generator 
built capable of producing alternations of so high a 
frequency. Only a very few such machines are in use 
to-day and those only at the very high-powered stations. 

As has been shown, an inductance-capacity circuit will 
oscillate and it is in this way that the radio frequency 
oscillations are secured. In order to get such a circuit 
to oscillate, it is only necessary to furnish it electrical 
energy. This energy must be furnished, then the source 
of energy removed from the circuit, and the inductance 



232 



EADIOTELEPHONY 



and capacity thrown in series in the circuit. This is 
done by the use of a spark gap. 

In figure 5, the source of high potential is charging the 
condenser as shown in the diagram. The two terminals 
(electrodes) of the spark gap (they are usually metal 
plates) are also being charged as they are in electrical 
connection with the source of potential. As the charging 
goes on both the condenser and the electrodes of the 
spark gap rise to a higher and higher potential. When 



FlCr.6. 




this potential reaches a certain high value it is strong 
enough to cause a spark to jump across the air gap of the 
spark gap. The instant this spark passes, the air gap 
changes its electrical character. Instead of being a very 
good insulator it becomes a fairly good conductor. The 
condenser and inductance therefore are thrown in series 
and oscillations take place in the circuit. 

The oscillations are confined to the condenser-spark- 
gap-inductance circuit, as the iron-core choke coil pre- 
vents their passage through that circuit. The choke coil 
has a very high self -inductance, due to its iron core. The 



MIRACLE OF THE AGE 233 

current of an oscillation changes very rapidly. As this 
rapidly changing current attempts to enter the choke 
coil the inductance of the coil opposes the flow of the cur- 
rent. So great is this opposing force of inductance that 
it altogether chokes off the oscillation. In a great many 
sources of high potential the inductance of the instrument 
giving this high potential is so large that no choke coil is 
needed. 

The oscillations that occur in the condenser-spark gap- 
inductance circuit are damped oscillations. That is, the 
oscillating current grows smaller with each oscillation. 
If we draw the hack-saw blade aside and then free it, the 
distance that it moves from the point of rest becomes 
smaller with each vibration until finally the blade ceases 
to move. This is because the moving blade loses energy 
in various ways. In exactly the same way the current of 
the oscillation dies away until there is no current, because 
the current loses energy. The way in which energy is 
lost will be shown later. The actual oscillations of the 
circuit are represented in figure 6. This represents a 
damped oscillation. As has been stated, a radio wave is 
exactly similar to the oscillations which produce it, there- 
fore figure 6 also represents a damped radio wave. The 
amplitude of a damped wave becomes smaller with each 
succeeding wave. 

SOURCES OF HIGH POTENTIAL. 

The usual way of furnishing the high potential to the 
condenser in the spark-gap circuit is by the use of an in- 
duction coil, or a transformer supplied by an alternating 
current generator. An induction coil works on a direct 
current. Figure 7 shows a diagram of the induction coil. 
The vibrator makes and breaks the primary circuit, thus 
inducing a high voltage in the secondary which is wound 



234 



EADIOTELEPHONY 



with many turns of fine wire. The vibrator contacts are 
adjustable by means of the set screw. The condenser 
across the vibrator contacts produces a higher voltage in 
the secondary than would be produced if it were not there. 
It also tends to prevent an arc forming at the vibrator 
when the circuit is broken there. 

When an induction coil is used to charge a condenser in 
a spark-gap oscillating circuit, the condenser is charged 
to a potential high enough to break down the spark gap 
each time the vibrator breaks the electrical circuit. The 




sudden stopping of the current in the primary produces 
a surge of high voltage in the secondary, thus charging 
the condenser. Figure 8 shows the relations of current 
and voltage in the primary and secondary. 

To read such diagrams it must be remembered that 
two things are always shown on such a diagram, and 
that moving to the right means an increase in one thing 
and moving upward means an increase in the other thing. 
In this case (fig. 8) moving to the right means an increase 
in time and moving upward means an increase in current 
in the upper part of the diagram, which represents the 



MIKACLE OF THE AGE 



235 



primary current, and an increase of voltage in the lower 
part of the diagram, which represents the secondary 
circuit. 

A study of this figure shows that at the "make" the 
primary current gradually rises until it reaches a value 
great enough so that the electromagnet core pulls the vi- 
brator from the contact, thus causing the break. Mean- 
while the secondary voltage has risen to a maximum in 
the negative direction, and has fallen nearly to zero value. 





/=/<?. 0. 




Time -. 

(A A 


i i 

i 
i 


i - 




|1 


1 

1 
1 
1 
i 

i 


1 I 




Time 


[^ 



At the break the primary current falls suddenly to zero. 
This sudden change in the magnetic lines of force cutting 
the secondary produces a very high voltage in the sec- 
ondary as shown in the figure. This voltage is the volt- 
age that charges the oscillating circuit to a potential high 
enough to break down its spark gap. Figure 8 represents 
the action of an induction coil with no capacity shunted 
across the vibrator and a high noninductive resistance 
connected across the secondary circuit. The action with 



236 



KADIOTELEPHONY 



a condenser across the vibrator, and with the secondary 
terminals connected to an oscillating spark-gap circuit, 
is more complex but similar in major details. 

A type of induction coil known as the buzzer trans- 
former is lately coming into use to charge the oscillating 
circuit from power derived from a low voltage direct 
current. Figure 9 shows a diagram of the connections 
of such a buzzer transformer. 

The buzzer, B, is attached to an electromagnet, NSN', 
which is pivoted and free to move. The circuit from the 



ncr.o. 






13 



z 



battery is divided, so that part of the current passes 
through the electromagnet, NSN', at all times, and a part 
of the current passes through the vibrator, B, and thence 
through either one of the two primary windings, EE or 
FF. The electromagnet, NSN', has the direction of its 
windings reversed at the middle point of the core, so that 
at each end of the magnet there is a north pole. 

There are two primary windings, one being wound so 
as to produce magnetic effects opposite in direction to 
the other. Each primary winding is split in two parts, 
as is also the single secondary winding. The iron core 



MIRACLE OF THE AGE 237 

on which the primary and secondary windings are wound 
has three projections, as shown, one near each end of the 
electromagnet and one near its center. The secondary, 
as usual, has a large number of turns while the primaries 
have a comparatively few number of turns. 

ACTION OF BUZZER TRANSFORMER. 

The action of the apparatus is as follows: Consider 
the vibrator B to rest on contact a, thus completing that 
part of the circuit. The current then flows through a, 
through the primary winding EE and from there back 
to the battery. This flow of current in the primary es- 
tablishes a magnetic field in the iron core on which it is 
wound. This magnetic field does two things : it passes 
through the secondary coil, thus inducing a high voltage 
in the secondary. It also has the effect of making the 
core projections P and T poles of a magnet, P being an 
effective north pole, and T, a south pole. Like poles 
repel and unlike attract, so that P pushes the N end of 
the electromagnet away from P and T pulls the N' end 
of the magnet toward T. The magnet, being pivoted, 
turns and carries with it the vibrator, B, which thus 
breaks the circuit at a and makes the circuit at c. When 
the circuit is made at c, the current flows through the 
other primary winding, FF, which it must be remem- 
bered is wound opposite in direction to EE. 

The magnetic field established by this current is op- 
posite in direction to the one established by the first pri- 
mary winding and therefore the high voltage induced 
in the secondary is opposite in direction to the first in- 
duced voltage. It is of equal intensity because the elec- 
trical characteristics of the two primary coils are the 
same. The magnetic field makes T an effective north 
pole and P an effective south pole, thus turning the 



238 KADIOTELEPHONY 

magnet so that it pulls the vibrator B away from the 
contact c and makes the contact at a. It is to be remem- 
bered that the part of the current flowing through the 
electromagnet, NSN', is a steady uninterrupted current. 
The condenser is connected across the vibrator to in- 
crease the efficiency of the apparatus and to reduce spark- 
ing or arcing at the break. 

ADVANTAGES OF A BUZZER TRANSFORMER. 

The buzzer transformer has many advantages over the 
induction coil. It is more than twice as efficient. It is 
capable of making and breaking each primary circuit 
500 times per second. The movement of the vibrator 
can be made to be exactly regular so that the high voltage 
in the secondary is induced at regular intervals of time. 
Also the induced voltage rises to the same values, both 
positive and negative. 

The alternating current generators used to charge the 
condenser in an oscillating circuit system are built to give 
a higher number of alternations per second than the al- 
ternators used on power lines. The frequency (com- 
plete cycles consisting of a rise to a maximum of voltage 
in one direction, a gradual fall to zero voltage, and then 
a rise to a maximum voltage in the opposite direction, 
followed by a fall to zero voltage) of the former is most 
commonly 500 per second, while that of the latter is usual- 
ly 60 per second. 

A special machine for the purpose is the inductor type 
alternator. In figure 10, ab and cd are iron forms. W is 
a disk, which has been cut away at the edges to leave the 
iron projection p. The distance between b and p and p 
and c is only a fraction of an inch. The disk "W revolves 
so that the space between b and c is alternately filled with 
a projection, p, and a slot s. A direct current passes 



MIRACLE OF THE AGE 



239 



through the coil wound on ab. This direct current sets 
up a magnetic field whose complete circuit is b, p, c, &, p, a, 
b. Thus it cuts through the coil Y wound on cd. As the 
wheel revolves, the magnetic circuit is changed as the 
projections, p, and the slots, s, come between b and c. 
The projections, p, being iron, allow a strong magnetic 
flux (field) to pass, the slots, s, being air or a nonmag- 
netic metal, permit only a weak magnetic flux to pass. 
This change in the magnetic flux passing through the coil 
Y induces in it an alternating current. 

The advantage of this type of machine lies in the fact 
that the revolving part can be made of solid metal so that 




it can be turned at a high rate of speed without danger of 
flying apart. By use of this style of generator, Alexan- 
derson has produced a machine which gives a frequency 
of 100,000 cycles per second. There are 300 slots in the 
inductor (wheel, W) which turns at a speed of 20,000 
revolutions per minute. The particular use of the Alex- 
anderson alternator will be shown later. Although the 
Alexanderson alternator is not used to charge a con- 
denser in a spark gap oscillating circuit, an inductor- 
type alternator giving a moderate frequency (around 
500 per second) is often used. 



240 KADIOTELEPHONY 

It has been shown so far what a wave is and the various 
terms used in describing waves; that a wave takes its 
characteristics from its source; that a radio wave is a 
wave in ether traveling with a velocity of 300,000,000 
meters per second; that radio waves are produced by- 
rapid to-and-fro movements of electrons (high frequency 
oscillations of current) ; that these oscillations will be 
produced in an electrical circuit containing inductance 
and capacity; that the frequency of the oscillations in 
the circuit, and hence the frequency of the resulting wave, 
can be varied by varying either the inductance or ca- 
pacity (or both) in a circuit; that a change in frequency 
of a radio wave makes a corresponding change in wave 
length so that the wave length is varied by varying either 
the inductance or capacity (or both) in the radiating cir- 
cuit. 

It has also been shown that in order to add effective 
electrical energy to a capacity inductance circuit, it is 
necessary to open the circuit while the condenser (ca- 
pacity) is being charged and then to close it; that this 
opening and closing of the circuit is done automatically 
by means of the spark-gap. Various instruments used 
in charging the condenser have also been described. 

THE ANTENNA. 

A high frequency oscillating current in a circuit will 
radiate waves, but it has been discovered that some forms 
of circuit will radiate much better than other forms. An 
air-cooled gas engine, such as on a motor cycle, has a 
specially formed cylinder so that it will radiate heat 
well; the radiator of a water-cooled-engine automobile 
has a special form so that it will radiate heat well. In 
the same way specially formed circuits are made to 
radiate the electric waves. They are of various types, 
but are all called antenna. The antenna then of a trans- 



MIRACLE OF THE AGE 



241 



mittiiig station is that part specially built to radiate the 
waves. 

An antenna usually consists of a ground connection 
and one or more wires elevated above the ground and 
insulated. The usual forms are the inverted L, the T, the 
V, and the umbrella, each of these terms being descrip- 
tive of the method of arranging the wires in the antenna. 
As it has been found that the wire arranged as antenna 
has capacity, another condenser in the antenna circuit is 
not a necessity. The antenna wire has inductance alsc, 



1 


^Altr-Antenna 
O Inductance . 















Sporh 
Gap 


T ! 


55. Battery 




-y Ground 


A 











but it is usual to add variable inductance in the form of 
a coil so as to be able to control the wave length. 

Lately there is coming into use antenna in the form of 
loops which are from 1 to 2 meters across their diagonal. 
Another form of antenna is a cylindrical coil of large 
dimension compared to the coils used in other parts of a 
radio set. Both the coils and the loops are less effective 
than the common form of antenna, and must be specially 
designed to give even fair radiation. 

It has been found that some forms of antenna radiate 

more energy in one direction than in another. This is 

similar to the fact that when a man uses a megaphone 

more sound energy is radiated in the direction in which 

16 



242 BADIOTELEPHONY 

the megaphone points than in any other direction. In 
the inverted L antenna more energy is radiated in the 
direction along which the horizontal wire or wires extend 
and toward the lead-in wire in that direction than in any 
other direction. In the V antenna more energy is radiated 
in the direction in which the V points than in any other 
direction. In the T antenna most energy is radiated in 
both directions along the line of the horizontal wires. In 
the loop most energy is radiated in both directions along 
the plane of the loop. 

It is well to think of the wires in the antenna (except 
in the loop and coil types) as one plate of a condenser. 
The other plate is the earth. Thus it is just as necessary 
to have the antenna wires well insulated as it is to have 
condenser plates well insulated. 

A SIMPLE TRANSMITTING SYSTEM. 

A transmitting system is shown in figure 11. The 
symbols used are standard. This is the simplest type of 
a transmitting equipment. The broken line divides the 
apparatus into two parts. Part A is the apparatus 
necessary to charge and control the charging of the con- 
denser in the spark-gap circuit. Part B is the radio fre- 
quency circuit. The arrow through the inductance de- 
notes that the inductance can be varied in value. It is to 
be remembered that the antenna furnishes the capacity 
in the spark-gap circuit. 

A study of the action of this apparatus will clarify 
ideas up to this point. Figure 8 depicts what happens 
in an induction coil when it is in action. It is to be re- 
membered that the high peaks of voltage in the secondary 
occur each time the vibrator breaks the circuit, which is 
usually about 400 times per second. As the secondary 
voltage of the induction coil mounts higher and higher, 



MIRACLE OF THE AGE 



243 



it charges the antenna circuit to a higher and higher po- 
tential. The potential finally becomes high enough to 
break down the spark-gap which allows the inductance- 
capacity circuit of the antenna to oscillate. This oscilla- 
tion takes place as shown in the lower part of the dia- 



FiG.lZ. 




i 


1 1 


i 


! 


1 




Tin 


i 
i 




1 


[ | 




i 


1 


L 




11 A aa ^^ n 


7 


'i/rte 


y^V/vv- 


yuv^ 




I 


I 



gram. Notice that the oscillations and hence the waves 
are highly damped. 

The unbroken serise of waves W-n is called a wave 
train. Immediately after the last wave of the wave train 
passes the spark-gap regains its nonconductive property, 
and hence when the next surge of high voltage from the 
charging apparatus begins to charge the spark-gap cir- 



244 



EADIOTELEPHONY 



cuit it must raise it to the same high voltage necessary 
in the first case to break down the gap. Events repeat 
themselves as long as the key is pressed down. 

Thus it is seen that when the key is pressed in part A, 
figure 11, there are 400 wave trains per second radiated 
from the antenna. If the buzzer contacts were changed 
so as to make the vibrator move 700 times per second, 
there would be 700 wave trains per second. This applies 
to any rate of vibrations. The number of wave trains 
per second is the same as the number of vibrations. 




If an alternating-current generator were used as the 
source of power (used in A, fig. 11), the number of wave 
trains would be twice the frequency of the alternations, 
for the spark-gap would break down at the highest posi- 
tive voltage and again at the highest negative voltage — 
that is, twice in one cycle. (Note. — Using an alternator 
it is possible to arrange circuits so that the breakdown 
does not occur is indicated above ; hence that statement is 
not always true.) 

In figure 12 the time scale used in the upper part of the 
diagram is vastly different than that used in the lower 
part. This has to be done or otherwise the whole train 
of waves would be represented by a figure no larger than 



MIRACLE OF THE AGE 



245 



a pencil dot. Figure 12 does not show the action in the 
charging voltage after the spark gap has broken down. 

A radiating circuit arranged as shown in figure 11 
radiates a great amount of energy, but it radiates a broad 
wave. This statement means that the radiant energy is 
not carried by a single wave length, but is carried by a 
broad band of wave lengths. Figure 13 shows this graph- 
ically. 

The wave length 300 carries the most energy which is 




represented by the length of the line ab; but in addition 
to that wave, there is a continuous band of waves having 
all possible wave lengths near the wave length of 300. 
Thus the wave whose length is 200 is radiated with an 
energy represented by the length of the line cd. Now, 
as only the energy represented by a very narrow band of 
wave lengths (shaded area around ab) can be received, 
all the other energy is wasted. 

For this reason and for another which will be taken up 
later it is very desirable to radiate all the energy at a 



246 EADIOTELEPHONY 

single wave length. No way has as yet been found to do 
this, but a method has been found to radiate waves so 
that a great part of the energy is at a single wave length 
and the rest of the energy is radiated in wave lengths 
very close to the main wave length. The curved line in 
figure 14 shows the practical result that can be obtained. 

The straight line shows the ideal kind of wave. Of 
course, if all the energy were put into this single wave, it 
would contain a very large amount of energy. To repre- 
sent this, the straight line would have to be drawn longer. 

The production of an impure wave (the broad band of 
wave length is sometimes spoken of as an impure wave) 
is not uncommon. A person gets a cold and becomes 
hoarse. His voice sounds hoarse because his vocal cords 
produce an impure wave. A man who is not a musician 
blows a cornet and produces a disagreeable sound. He 
has produced an impure wave. Training and practice 
will enable him to produce a pure wave. Allow a bell to 
fall, it make a noise, that is, it gives forth an impure 
sound wave. Strike the bell with a clapper and it gives 
forth a clear musical sound — a pure wave. 



CHAPTER XXV. 



A Typical Spark Transmitting Circuit — Spark Gaps — 

Oscillation Transformers and Coupling — Tuning of a 

Circuit — Damping. 

To produce a nearly pure wave, it has been found nec- 
essary to add another circuit in a radio transmitter to 
the one shown in figure 11 in the preceding chapter. 
This is shown in figure 15, which is a typical diagram of 
a transmitter. It shows three distinct circuits which have 
been divided by broken lines in the diagram. Circuit A 



^ 


7 


FtG. IS. 


A 






t?**l 




c 

- 


r 


1 3 



is the power circuit. Circuit B is the spark-gap circuit. 
Circuit C is the radiating circuit. 

Note that the inductance in both circuits B and C is 
variable as shown by the method of having an arrow 
point on the wire leading to it. This method of showing 
variable inductance, and also variable resistance is fre- 
quently used. 

Circuit C is coupled to circuit B by means of the in- 
ductance in circuit C, which is shown opposite to the in- 
ductance in circuit B. These two inductances together 

247 



248 RADIOTELEPHONY 

form an oscillation transformer. The name is given 
because it transfers oscillations from one circuit to an- 
other. In an oscillation transformer the oscillations in 
one circuit are transferred to the other circuit. There 
may or may not be a change in voltage. Thus, in circuit 
C there is induced, by means of the oscillation trans- 
former, oscillations of the same frequency that occur in 
B. 

A study of the action of the circuits in figure 15 shows 
more clearly the function of each. A special spark-gap 
is supposed to be used in circuit B. Circuit A furnishes 
the power to circuit B, which acts as a trigger circuit. It 
stores up the energy until the spark gap breaks down and 
this breaking down allows the oscillations to occur. 
These oscillations are transferred to circuit C where 
they are radiated. Figure 16 shows this. 

It is to be noted that the radiated wave train shown in 
figure 15 contains many more waves than the radiated 
wave train shown in figure 12 in chapter XXIV. Circuit 
C has a long wave train because it has no spark gap. A 
spark gap, even after it breaks down, has considerable 
resistance, and resistance in a circuit quickly dampens 
out a wave, thus giving only a few waves to a wave train. 

SPARK GAPS. 

Figure 16 shows the action in the circuits when a spec- 
ial spark gap is used. If there were not a special spark 
gap the oscillation transformer would be in action all the 
time, and having transferred the oscillations from circuit 
B to circuit C, would retransfer them back to circuit B 
and thus reduce the energy in circuit C. This transfer 
and retransfer would take place several times before the 
waves died out. If this happens, of course a great deal of 



MIRACLE OF THE AGE 249 

the energy is wasted in the spark-gap circuit instead of 
being radiated from the antenna circuit. 

There are two types of spark gaps in common use 
which prevent this retransfer of energy. Eenergy can 
not get back in the B circuit if that circuit is broken im- 
mediately after it has transferred its energy to the an- 
tenna circuit. In other words, no oscillations can be set 
up in a broken circuit. Both types of spark gap work on 
this principle. 



i 



i 
i 

—21 



Fig. 16. 

5pork Gap Break Dch/n 



Time 



3 t 



Time 



Oscillation in Circuit 3. 



RadtQted Oscillations in Circuit C. 
Hence also represents Rodiated Wove. 



Time 





One type does this by electrical action. Instead of only 
one gap, there are a number of gaps placed in series. 
The electrodes of the gap are broad pieces of metal ac- 
curately ground to a smooth, even surface. There is a 
groove around each plate, and the plates are separated 
by the mica rings. Figure 17-A shows this type of gap. 
The flange assists to keep the plates cool. Sometimes a 
fan is used also for this purpose. This arrangement is 
called a quenched spark gap, and it has the property of 
recovering its nonconductance in a very short time, that 
is, after only a few oscillations have passed. 



250 



BADIOTELEPHONY 



The other type is the rotating spark gap. Figure 17-B 
shows the principle of such a spark gap. There is a ro- 
tating metal wheel carrying the metal projections a. As 
the projections approach the ends b of the circuit, they 
get near enough for the spark to pass. The rotation of 
the wheel carries the projections past b and gradually 
make the gap longer, so that it soon becomes too long to 
carry the oscillations. Thus only a few oscillations are 
permitted to pass. If the wheel is made to rotate at such 
a speed that a approaches b each time the secondary of 
the changing circuit (A, fig. 15) reaches its high voltage, 




the gap is said to be synchronized. If no provision is 
made to obtain this, the gap is called a nonsynchronous 
gap. 

In practical operation the appearance and sound of 
the spark gap when the spark is passing tells much about 
the operation of the set. Spark gaps are usually adjust- 
able. The spark should occur regularly (told by the 
sound) and should give bluish-white stringy sparks. A 
yellowish color indicates an arc instead of a spark. If an 
arc is established in the gap, the efficiency of a set is much 
reduced. A set works best when the longest gap giving 
regular sparking is used. 

As has been noted, an oscillation transformer transfers 
by electromagnetic induction oscillations from one circuit 



MIRACLE OF THE AGE 



251 



to another. Whether or not there is a change in voltage 
of these oscillations depends upon the capacity, induc- 
tance, and resistance of each circuit. There are various 
types of transformers in use. However, they have the 
same general characteristics, that is, an induction in one 
circuit always acts upon an inductance of the other cir- 
cuit. Figure 18 shows some of the types in use. A repre- 
sents two coils of wire, one larger than the other, and 
both mounted on the same axis, along which one is mov- 




able. The smaller one can be slid into the larger one. 
It is commonly termed a loose coupler. B shows a flat, 
spiral type whose coils can be made to approach each 
other. C shows an arrangement for mounting the flat 
spirals and moving them on a hinge at H. D shows two 
coils, the small one mounted inside the other. The inside 
one can be rotated around an axis, so that it can be made 
to be at any angle with the outside one. 

"When one circuit acts in any way upon another circuit, 
the two circuits are said to be coupled. In figure 15 cir- 



252 



RADIOTELEPHONY 



cuits B and C are coupled. An oscillation transformer 
always couples two circuits together. Another method of 
coupling circuits is shown in figure 19. An arrangement 
such as this is called an autotransf ormer. Other methods 
of coupling are used in receiving circuits and will be dis- 
cussed later. 

It is to be noted that each type of transformer shown 
above contains a variable factor. This variable factor is 
for the purpose of varying the degree of coupling. If one 
circuit acts with considerable force upon another circuit, 
the coupling is said to be close or tight. If one circuit acts 




with very little force upon the other circuit, the coupling 
is said to be loose. All degrees of coupling between close 
and loose are possible. 

The following example will illustrate more fully how 
various degrees of coupling are possible. Suppose it was 
desired to swing an occupied hammock. This could be 
done by attaching a cord to the hammock and pulling 
the cord at the proper time. The cord acting upon the 
hammock acts with considerable force — it represents a 
tight coupling. Instead of using a cord, replace it with 
a light elastic band. Pulling upon the elastic band at the 



MIRACLE OF THE AGE 253 

proper time will cause the hammock to swing, but it will 
take many more pulls than with the cord, for the force 
acting upon the hammock at each pull is very small. This 
represents a loose coupling. 

In the oscillation transformer the degree of coupling 
is varied by moving the inductances with respect to each 
other. Coupling is the tightest when the coils are parallel 
and as close together as possible. If the coils are moved 
farther apart, or if they are moved at an angle with each 
other, the coupling is made looser. The loosest coupling 
is obtained when the coils are at right angles, or when 
the coils are as far apart as the design allows. In the 
autotransformer the coupling is varied by varying the 
position of the contacts b and c (fig. 19). The fewer coils 
between these points, the looser the coupling. 

A change in the amount of inductance in either part of 
the coupling transformer varies the degree of coupling, 
as does also a change in the rapidity with which the os- 
cillations of either circuit are damped. But these factors 
are not taken into account, because the latter is a part of 
the design of the apparatus and the former, if changed 
at all, is done for the purpose of tuning, and not for the 
purpose of varying the degree of coupling. 

TUNING OF CIRCUIT—RESONANCE. 

It has been shown that the frequency of oscillations oc- 
curring in a circuit depends upon the values of the ca- 
pacity and inductance of the circuit. A change in either 
or both will change the frequency of oscillations. The fre- 
quency referred to is the natural frequency of the circuit. 
It is possible to produce oscillations in a circuit with a 
frequency other than the natural frequency, but these are 
forced oscillations, the force coming from without the 
circuit. In the same way a suspended ball has a natural 



254 



EADIOTELEPHONY 



frequency of swing, but it is possible to cause it to swing 
at another frequency by an outside force — moving it back 
and forth with the hand, for example. 

To change the natural frequency of a circuit it is neces- 
sary to change either the capacity or inductance, or 
both. When this change is being made in a circuit to 
make its frequency agree with that of another circuit, it 
is called tuning the circuit. If one circuit is tuned to 
another, resonance exists between them. Eesonance, 
then, exists between two circuits if their natural fre- 



I 


b 
dl j \ 

i | 
c! I* 




Wave Length 



quencies are the same. This condition of resonance must 
exist between circuits coupled together in any way if 
there is to be an efficient transfer of energy. 

The fool who rocked the boat understood the principle 
of resonance. He found that by swaying his body from 
side to side at a certain frequency he could set the boat 
rocking through a wide arc. In other words, he made the 
frequency of his swaying equal to the natural frequency 
at which the boat rolled and thus secured a large effect. 
In the same way, in making a child's swing move, if it is 



MIRACLE OF THE AGE 255 

pushed at the proper time it can be made to swing very- 
high, but only by properly timed pushes. Being properly 
timed (in resonance) each push adds its energy to the 
energy already in the swing. Another example is in 
practicing with the punching bag. If each blow is timed 
the bag is kept moving in a regular way. Get out of time 
(out of resonance) and the bag will move irregularly. 

So in circuits that are coupled together. If they are 
not in resonance the effect of one on the other is very 
little. If the circuits are in resonance very much energy 
is transferred from one to the other. So that, when cir- 
cuits are coupled it is necessary to have them tuned to 
each other in order to transfer energy from one to the 
other. 

A study of figure 20 shows clearly how the energy will 
vary in a circuit as it approaches resonance. The curve 
shows the energy in the secondary circuit as its LC value 
(induction capacity value) was being changed. At a, it 
had the same LC value as the primary circuit, there- 
fore was tuned to that circuit. The energy transferred 
to the circuit is the greatest at that point. It is repre- 
sented by the length of the line ah. At c the circuit was 
slightly out of resonance (tuning not exact) and the 
amount of energy it received is represented by the length 
of the line cd. The circuits used in obtaining the data for 
this curve were loosely coupled. 

DAMPING— EFFECTIVE RESISTANCE. 

An oscillating current once started in a circuit would 
continue oscillating indefinitely if it did not lose energy. 
But a loss of energy always takes place and hence the 
oscillations die away — it is a damped oscillation and 
gives rise to a damped wave. The measurement of this 
damping is called the decrement of the wave. Thus a 



256 KADIOTELEPHONY 

wave having a decrement of 0.2 dies away much more 
quickly than a wave having a decrement of only 0.01. 

The losses in the antenna circuit are due to the ohmic 
resistance of the wires ; to the fact that currents are in- 
duced in the earth near the antenna and in neighboring 
circuits ; to the leakage of the charges of electricity, and 
to the energy expended in radiating the waves. The 
latter is of course desirable, as it is the purpose for which 
the antenna is constructed. All the other losses mean 
wasted energy, so it is desirable to make these losses as 
small as possible. 

SET RADIO STATION AWAY FROM TREES. 

The loss by induced currents in neighboring circuits 
should be taken care of in the design of a transmitting 
set. The use of a quenched spark reduces this loss as 
the quenching effect quickly breaks the primary circuit. 
Presence of trees and other objects may make a circuit 
which will absorb energy by having induced currents 
established in them. Aside from this, trees absorb en- 
ergy from the radiated wave so that it is well not to set 
up a radio station near a tree or trees. 

A certain amount of electricity will leak off: the wires. 
This can be cut down by having no sharp ends and by 
taking great care to have proper insulation. A frequent 
source of such leakage in portable sets is in the wires 
themselves, where they become frayed and the loose ends 
of strands project. 

The ohmic resistance is the resistance of the wire itself 
which gives rise to heat. It is oftentimes called the Jou- 
lean resistance — Joulean referring to heat. It has been 
found that when oscillations at radio frequency are flow- 
ing in a circuit, the ohmic resistance is much greater than 
when a direct current flows in the same wire. An increase 



MIRACLE OF THE AGE 257 

in frequency of the oscillations gives an increased resis- 
tance. The explanation of this increased resistance lies 
in the fact that the self-induction of the high frequency 
currents allows a current to flow only on the surface of 
the wire. This is, in effect, the same as reducing the cross 
section of the wire, thus increasing the resistance. For 
this reason a wire used in a radio circuit should have a 
large surface. Wire made up of small strands gives a 
large surface without materially increasing the diameter 
of the wire. Stranded wire is, therefore, generally used. 
It must not be overlooked that the ground is a part of 
the antenna system. Therefore the ground resistance is 
a part of the antenna resistance. Thus great care must 
be taken to keep the ground resistance as low as possible. 
This is done by driving into the ground a number of 
metal stakes and connecting them together; by burying 
metal mats ; and by the use of a counterpoise. A counter- 
poise of an antenna consists of a number of conductors 
stretched under the wires forming the antenna, and in- 
sulated from the ground. This is used instead of the 
ground. In an airplane, the metal parts of the plane are 
connected electrically and form a counterpoise. In a 
ship, the metal plates of the ship form the counterpoise. 
In some cases in land station, no precaution is taken to 
insulate the counterpoise wires from the ground. 

RECEPTION OF DAMPED WAVES. 

It has been shown that radio waves consist of ether 
waves having electrostatic and electromagnetic lines of 
force. A method of producing damped waves of this 
character has been described. These waves travel 
through space and are detected by means of special ap- 
paratus. Much of this special apparatus is similar to that 
used in the transmitting station as will be noted. The ac- 



258 



RADIOTELEPHONY 



tion that takes place at a receiving station may be briefly 
summed up as follows: The received waves set up an 
oscillating current in the receiving circuit that has the 
same frequency as that from which the wave started. 
These oscillations are changed in character so that they 
will actuate a telephone receiver, thus making an audible 
signal. 

In the circuit which receives the waves is the antenna. 
It is exactly like the antenna used in the transmitting sta- 
tion, and in most stations the antenna that is used for 
transmission is used also for reception. Considering only 
the electromagnetic lines of force in the wave, the oscilla- 




te.,?/. 




»fr 



Telephone 
(fif Receiver* 



tion induced in the receiving antenna is caused by electro- 
magnetic induction. This is the same phenomena that 
occurs in the induction coil, the transformer, and various 
other instruments. 

Considering the electrostatic lines of force, it must be 
remembered that these lines are the result of potential 
and that they will induce a potential on any conductor 
which they sweep. They sweep the antenna and thus in- 
duce a potential on it. As the intensity of the impinging 
electrostatic lines of force varies and changes in direction, 
the resulting potential varies and changes in direction ; 
that is, it is oscillating and has the same frequency as the 



MIRACLE OF THE AGE 259 

impinging wave. The electromagnetic and electrostatic 
lines of force are inseparable in a wave and it is their 
combined effect which produces the oscillation in the re- 
ceiving antenna. 

A simple type of receiving circuit is shown in figure 21. 
Note that circuit C is the same as circuit C in the trans- 
mitting circuit. (See fig. 15.) That circuit B is also the 
same except that it contains no spark gap. Circuit A is 
the circuit distinctive of the receiving apparatus. 

OPERATION OF TELEPHONE RECEIVERS. 

A telephone receiver transforms alternating currents 
or pulsating direct currents into sound. It does this by 
means of a small electromagnet placed in rear of a thin 
round piece of iron, called the diaphragm, which is held 
around its edge. As each pulse of current (or each alter- 
nation in an alternating current) passes through the elec- 
tromagnet the electromagnet pulls the center of the dia- 
phragm inward. As the pulse of current passes the stiff- 
ness of the diaphragm causes the diaphragm to spring 
back. Another pulse of current again pulls the dia- 
phragm inward, and so on. Thus the diaphragm vibrates 
with a frequency equal to the frequency of the pulses of 
current. This vibration of the diaphragm causes the air 
to vibrate, thus giving rise to sound. These vibrations 
must have a frequency within the limits 30-3,000 per sec- 
ond in order to be plainly heard. Thus frequencies within 
these limits are called audio frequencies. 

A telephone receiver cannot be inserted directly in a 
radio-frequency oscillating circuit for the reception of 
signals. The reason for this is that the diaphragm of the 
receiver is not capable of vibrating with the rapidity of a 
radio-frequency oscillation which it has previously been 
stated must equal 6,000. Even if it were capable of this 



260 



RADIOTELEPHONY 



high rate of vibration, the human ear would not respond 
to such a high frequency. Thus some method of changing 
the oscillations is necessary. This is done by means of a 
detector. 

It has been discovered that certain materials — galena 
crystal, for example — have a peculiar electrical property. 
They allow the passage of a current of electricity through 
them in one direction, and will not allow a current to pass 



i 

! 


4 i 

1 

P St 


Fi&ZZ. 
B 


r\ r\ r\ 







in the opposite direction. Thus in figure 22-A the de- 
tector will allow a current to pass downward through it as 
shown by the arrow but will not allow a current to pass 
upward through it. If a detector is put in a circuit hav- 
ing alternating current of the usual form (upper part of 
B, fig. 22) the resulting current passing through the cir- 
cuit would be as shown in the lower part of B (fig. 22). 
This is because that part of the current which would 
usually flow in the direction represented below the line is 
not allowed to flow because of the action of the detector. 
Thus in figure 21 the impinging waves set up oscillations 
in circuit C. These oscillations are transferred to the 
circuit B, which contains inductance and capacity, and 
will therefore oscillate when tuned to circuit C. There- 
fore at g, in circuit A, there is an alternating voltage as 
that point is directly connected with circuit B. This al- 



MIRACLE OF THE AGE 



261 



ternating voltage agrees in frequency with the frequency 
of oscillations in circuit B, since it is produced by these 
oscillations. As has been noted in the above paragraph, 
the detector allows the passage of a current in only one 
direction and hence only the voltage in this direction is 
effective. The result is that there is a pulsating direct 



F/G.Z3. 


! + 


iAAaa. »■-— Mtu>. 


Vyj/iA J (j|H/^ 


<ss- 




© js 

^1 






Ml ** — ► a/1a«» 




1! 


f\— f\ 


*! 





current flowing in circuit C. The pulsations occur at the 
radio frequency of the oscillation in circuit B. 

A study of figure 23 will aid in understanding the action 
of the receiver. The upper curve represents the oscilla- 
tions that occur in circuit B and, as has been stated, the 
voltages that present themselves at point g in circuit A. 
Because of the action of the detector, one-half of the oscil- 
lations are cut out so that there remains a pulsating di- 
rect current as shown in the middle curve. The telephone 
has a very high inductance. This inductance and the 
inertia of the telephone receiver causes this pulsating di- 



262 KADIOTELEPHONY 

rect current to act as a single surge of current as shown 
in the lower curve. Each surge of current pulls the tele- 
phone diaphragm inward. Figure 23 shows only two 
surges of current, but in a dot of the Morse code there are 
from 30 to 50 surges, thus causing the diaphragm to vi- 
brate from 30 to 50 times. This produces a sound. 

It is to be particularly noted that it takes a complete 
wave train to give one vibration of the telephone dia- 
phragm. For example, for a certain moderate damping, 
there are 40 effective waves in the wave train. These 40 
waves establish one surge of current through the tele- 
phone receiver. Thus the radio frequency waves give rise 
to audio-frequency pulses of current. 

A small condenser is sometimes shunted across the tele- 
phone receiver. This condenser is charged with every 
pulse of the high frequency current shown in the middle 
curve of figure 23. It discharges through the telephone 
receivers in the interval between pulses. This has been 
found to increase the effect upon the diaphragm of the 
telephone receiver. However, such a condenser is not a 
necessary part of the receiving apparatus and is some- 
times omitted with special kinds of telephone receivers. 



CHAPTER XXVI 

Other Methods of Coupling — Why Tuned Circuits Are 
Necessary — Resistence — Interference. 

IN addition to the methods of coupling described with 
relation to transmitting circuits, in the last chapter 
there is also another type sometimes used in receiv- 
ing circuits. This is called electrostatic coupling, as it 
depends upon the linking of electrostatic lines of force in 
two circuits to transfer the oscillations instead of the 
linking of electromagnetic lines of force. In electrostatic 
coupling, one set of plates of a condenser is in one circuit 




A 



Fig. 24-. 



5 




w 



and the other set of plates of the same condenser is in the 
other circuit. Figure 24 shows two methods of electro- 
static coupling. The inductance and capacity of each cir- 
cuit is marked; the unmarked condensers are the con- 
densers used in coupling the circuit. There are various 
other methods besides those shown. Electrostatic cou- 
pling takes the place of an oscillation transformer. Such 
an arrangement of circuits may be called an electrostatic 
transformer. 

263 



264 



BADIOTELEPHONY 



A radio wave is started by the transmitting apparatus. 
This transmitting apparatus has two distinct radio cir- 
cuits — B and C as given in figure 15. Both must be tuned 
to the same wave length (frequency) to give the best re- 
sults. The radio wave travels through space and induces 
an oscillation in any antenna which is tuned to that wave 
length — that is, the receiving antenna must have its in- 
ductance and capacity adjusted so that its natural fre- 
quency of oscillations is equal to the frequency of the 
wave which it receives. The oscillations in the receiving 
antenna are then transferred by some form of coupling 
to another oscillating circuit, which in turn must be tuned 





Fia.Z5. 


1 
1 




© 

o 

* 




Wove Lenq+h 



to the antenna receiving circuit. The detector and tele- 
phones are shunted on this second circuit. 

Thus the total number of tuned circuits in the transmit- 
ting and receiving instruments is four. The desirability 
of two circuits in the transmitter has already been partly 
explained. Additional reasons for these two circuits and 
for two receiving circuits are shown in the discussion 
below. 

It has been stated that a circuit containing a spark gap 
radiates a broad wave. The broad wave contains a great 
deal of energy, much of which is useless, inasmuch as it 
cannot be utilized by the receiving station. Hence sta- 
tions are designed to transmit as sharp a wave as possi- 



MIRACLE OF THE AGE 265 

ble. Another very important reason for designing sta- 
tions to transmit a sharp wave is to prevent interference 
between stations. This is very important, as the number 
of radio stations is constantly increasing. The sharper 
the wave radiated the less interference it gives to stations 
not desiring to receive this wave. 

SHARP WAVES IN TRANSMITTING. 

This is illustrated in figure 25. A station is radiating 
a broad way of the shape shown. The most energy is con- 
tained in a wave whose length is 1,200. Figure 25 also 
represents the distribution in wave lengths of the energy 
of the wave. This energy reaches the receiving station of 
this set. But it also reaches and affects all other receiv- 
ing stations. Suppose, now, that two entirely distinct 
stations were trying to work on a wave length of 900 
meters, at the same time the 1,200-meter station was 
transmitting. They could not do it, because the station 
working on 1,200 is also radiating at 900. Hence the re- 
ceiving station for the 900 is picking up energy from both 
sending stations. Of course the result is a jumble of dots 
and dashes in the receiver with no meaning to them. That 
is, the receiving station is hearing the dots and dashes of 
the two transmitting stations and cannot distinguish be- 
tween them. 

This condition would apply not only to the 900-meter 
station but to all stations trying to work with a wave 
length anywhere near 1,200 meters. Thus it is desirable 
to transmit the very sharp wave shown in figure 14, Chap- 
ter XXIV. This is a sharp wave and carries most of its 
energy at wave lengths very close to the peak wave length 
represented by the vertical line — 1,200 in this case. With 
such a wave it is possible for stations to work without 
interference on wave lengths very close together. In 



266 RADIOTELEPHONY 

practice the wave lengths must be separated at least by a 
5 per cent, difference. That is, two stations, one at 1,200 
meters and one at 1,120 could work without interference, 
but it would be impossible for two stations, one at 1,200 
meters — the other at 1,195 meters to work without inter- 
ference. The narrower the curve (fig. 14) the nearer to- 
gether in wave lengths can stations work without inter- 
ference. 

AVOIDING INTERFERENCE. 

The main reason that two circuits are placed in the re- 
ceiving station (as shown in circuit C and B, fig. 21) is to 
avoid interference. Each circuit makes a selection of 
wave-length energy from the received waves and thus the 
final energy is nearly all of one wave length. A compari- 
son of this action would be as follows : It is desired to 
pick the best drilled squads from a company. One in- 
spector watches the company drill and eliminates certain 
squads. The remainder of the squads appear before a 
second inspector. This inspector eliminates certain 
squads and hence the retained squads are the best drilled 
squads as a result of this double selection. So in the re- 
ceiving station each circuit eliminates the energy of cer- 
tain wave lengths and the result is that only the energy 
of a very narrow band of wave lengths arrives at the 
detector. 

The curves shown in figure 26, in addition to the curves 
of previous figures, will give a more comprehensive view 
of the whole subject of interference, resonance, and cou- 
pling. The three curves shown in figure 26-A show the 
variation of the energy received at different wave lengths 
with a variation in coupling. Thus the lengths of the lines 
ah, a V , and a"b" represent the energy received at the wave 
lengths 1,120, 1,200, and 1,280, respectively, when the 



MIRACLE OF THE AGE 



267 



coupling is correct. The length of the lines ac, a'c, and 
a"c" represents the energy received at the same wave 
length when the coupling is too close. The double hump 
curve marked "Coupling too close" would be obtained 
with close coupling in any receiving set. Note that there 
are two frequencies (wave lengths) that receive a large 



6 



Correct- Coupling 




Coup// n a too c/ssc 



'Coupling too loose 



1120 1200 1260 

Wave Length 

FiaZGrb 

c 




TUN 

Frequency 



amount of energy. The explanation of this lies in the fact 
that an oscillating circuit coupled to another oscillating 
circuit is affected by the circuit to which it is coupled. It 
has two frequencies at which it will oscillate well. One of 
these frequencies is slightly higher and the other slightly 
lower than its natural frequency when oscillating alone. 
The closer the coupling the farther apart are these two 



268 EADIOTELEPHONY 

frequencies of oscillation. These circuits are tuned to 
each other ; that is, the inductance-capacity value of one 
is equal to the inductance-capacity value of the other. 

As is shown in the figure, the result of this double oscil- 
lation is to give the circuit a wide band of wave lengths 
from which it will absorb energy. This band can be nar- 
rowed by making the coupling just right. The result is 
shown in the curve marked "Correct coupling.' ' Care 
must be taken not to make the coupling too loose or the 
full energy will not be transferred from one circuit to the 
other. This is shown in the curve marked ' ' Coupling too 
loose." 

Figure 26-B shows the resulting energy absorbed by a 
circuit as it was tuned to another circuit to which it was 
coupled. At T it was out of tune — at U it was tuned — at 
N it was out of tune. The closer to U, the nearer tuned it 
was. Thus any of the three curves shows that the great- 
est energy was absorbed when the circuit was in tune with 
the circuit from which it received its energy. 

RESISTANCE HINDERS SHARP TUNING. 

The three different curves in B represent the same 
thing for three different circuits just alike except that A 
has a high resistance, B a medium resistance, and C a low 
resistance. Thus it is seen that the circuit having the 
least resistance has a sharp well-defined point at which it 
is tuned. Eesistance in a circuit decreases the possible 
sharpness of tuning in the circuit as well as making a 
damped wave when the circuit is radiating. 

The curves in A and B of figure 26 represent energy 
absorbed by a circuit when coupled with another circuit. 
The same identical curves would represent the energy 
radiated by the same circuits. Thus a circuit closely cou- 
pled with another circuit would radiate a broad band of 



MIRACLE OF THE AGE 269 

wave lengths with two prominent wave lengths. If a 
quenched spark is not used in a damped-wave transmit- 
ting station, this condition applies. A circuit of high 
resistance will radiate a broad band of waves, as has al- 
ready been noted in a radiating circuit containing a spark 
gap. 

To sum up, it is desirable to radiate energy confined to 
nearly a single wave length for (a) only this energy is 
useful in reception; (b) in order to avoid interference 
with other stations. This is done by having two tuned cir- 
cuits, one with a quenched gap. These two circuits should 
have the proper degree of coupling. They should have as 
low resistance as it is possible to attain. It is desirable to 
have two circuits in the receiving station, in order to 
eliminate the effects of other waves than those which it is 
desired to receive. This elimination is best effected by 
two loosely coupled tuned circuits, with resistance as low 
as possible. 

CAUSES OF INTERFERENCE. 

In receiving there may be interference due to other 
causes than transmitting stations. This is due to the 
antenna being swept by waves caused by the forces of 
nature (thunderstorms, etc.). Also the antenna may re- 
ceive direct static changes due to the presence of charges 
upon surrounding objects including the air. All of these 
strays cause oscillating currents in the antenna and thus 
produce noises in the receiver. Their effect upon the 
antenna is similar in character as the effect of a heavy 
blow upon a child's swing. A heavy blow would cause the 
swing to swing back and forth even though it were not 
timed to the period of the swing. A circuit caused to 
oscillate in this manner is said to receive " shock' ' excita- 
tion. Having a second circuit in the receiving station 



270 EADIOTELEPHONY 

considerably reduces the noise in the receivers caused by 
these strays. The term static is oftentimes used to in- 
clude the cause of all sounds in the receiver not due to a 
transmitting station. 

DISTANCE AFFECTS INTERFERENCE. 

Whether or not interference will occur among stations 
depends not only upon the factors outlined above but also 
upon their distance apart. For instance, a small-powered 
station in Kansas would not interfere with stations in 
New York even if it were working on the same wave 
length. This is because the radio waves get weaker the 
further they travel. They eventually become too weak to 
affect a receiving station. There are many factors affect- 
ing the distance to which a radio wave will carry its en- 
ergy. It will carry energy further over sea than over 
land ; further over some kinds of soil than over others. 
A radio wave casts shadows. If a transmitting station is 
at the foot of a hill or mountain, a receiving station on 
the other side of the hill or mountain will receive very 
faint signals because of this shadow effect. Trees and 
buildings absorb the energy of the wave so that the plac- 
ing of either a receiving or transmitting station among 
them reduces the distance at which communication may 
be maintained. Other factors, such as the time of day, 
and the climatic conditions have various effects upon the 
distance at which communication can be maintained. 

DAMPED AND UNDAMPED WAVES. 

A damped wave is originated by an oscillating body 
whose oscillations are gradually fading out. In radio 
this gradual fading out of an oscillation means that the 
current of the oscillation gradually decreases in value. 
An undamped wave is originated by an oscillating body 



MIRACLE OF THE AGE 271 

whose oscillations always retain their maximum value. 
In radio this means that the current of the oscillation al- 
ways retains its maximum value. Thus in an undamped 
radio set the oscillation, and hence the wave generated by 
the oscillation, is continuous as long as power is applied 
(as long as the key is held down). This means that there 
are no wave trains in undamped waves as there are in 
damped waves. An undamped wave is also a continuous 
ivave, but a continuous wave is not necessarily an un- 
damped wave. Any unbroken wave is a continuous wave. 
This continuous wave may vary in amplitude. Continu- 
ous waves are those used in radiotelephony. 

ADVANTAGES OF UNDAMPED WAVES. 

To produce an undamped wave it is necessary to add 
energy to an oscillating body as fast as that body loses 
energy. For example, a child's swing once started will 
gradually come to rest. It loses energy due to the friction 
of the air; the friction of the ropes where they are at- 
tached to the support, etc. If it is desired to keep it 
swinging through a constant arc, a push must be given it 
at each swing ; this push adding just the same amount of 
energy as was lost during the swing. So in electric oscil- 
lation the current decreases because it loses energy by 
radiating some in the wave ; by the resistance of the wire 
causing heat losses, and by losing energy to other circuits 
and objects. To keep the current constant, it is necessary 
to furnish just the same amount of energy during each 
oscillation as is lost in that oscillation. There are various 
methods of doing this and these will be described later. 

Undamped waves have certain advantages over damped 
waves for use in radio communication. They carry much 
more energy in the same amount of time. For instance, 
suppose a dot used in radiotelegraphy last one-twentieth 



272 RADIOTELEPHONY 

of a second. Using a wave length of 1,500 meters, there 
would be in undamped wave transmission, 10,000 waves 
in this dot. If this dot was sent by damped waves there 
would be, if a spark discharge occurred 1,000 times a sec- 
ond, 50 wave trains in the dot. If each wave train con- 
sists of 40 waves — a reasonable number — the total num- 
ber of waves in a dot would be 2,000. Thus there are five 
times as many waves in the undamped wave dot as in the 
damped wave dot. But the damped wave has only one of 
its waves at maximum amplitude and the rest gradually 
die away while the undamped waves have every wave at 
maximum value. For this reason, the energy of each un- 
damped wave is in this case about five times the average 
energy of the damped wave, providing the maximum 
amplitude of the damped wave has the same value as the 
undamped wave's amplitude. Thus the energy in a dot 
carried by the undamped wave is 25 times the energy in 
a dot carried by the damped waves. This is a great ad- 
vantage especially as it does not take much more power 
to generate the undamped waves than it does to generate 
the damped waves. 

An undamped wave is a very pure wave and therefore 
has none of the disadvantages of a broad wave. These 
disadvantages have already been discussed. Because of 
the reasons stated in the preceding paragraph, the maxi- 
mum steady energy of an undamped wave need not be 
nearly so large as the initial energy of a damped wave to 
establish communication over the same distance. A di- 
rect result of this is the fact that voltages used in un- 
damped waves are not nearly so high as in damped waves, 
thus making easier the design of the instruments. Still 
another advantage is in receiving, as will be explained 
later. 



MIRACLE OF THE AGE 273 

One method of generating an undamped wave is by the 
use of the Alexanderson alternator described in Chapter 
XXIV. This alternator is capable of generating alternat- 
ing currents of radio frequency. The energy lost in each 
oscillation is therefore supplied direct by the generator. 
There are other generators that are capable of generating 
radio-frequency oscillations. Prominent among these are 
the Goldschmidt's machines. As the output of these gen- 
erators are radio-frequency oscillations, the output cur- 
rent may be fed directly to the antenna. However, this 
is not usually done because of the necessity to control the 
radiation from the antenna in order to give the dots and 
dashes used in telegraphy. The arrangement for doing 
this varies in different sets and is usually more or less 
complex. There must be some special arrangement to 
control the speed of rotation of these machines. The 
speed of rotation controls the frequency, and if this varies 
it changes the wave length, hence the speed must be kept 
constant. As the speed is very great, the speed-control 
system is quite complex. Owing to the great expense, 
these alternators are not used except at high-powered 
stations, and only a few of each type are in use at the 
present time. 

ARC TRANSMITTERS. 

Another method of generating undamped waves is by 
means of the arc. The arc transmitters are less costly 
than the alternators mentioned above, and there is no 
difficulty in controlling the wave length, as this is deter- 
mined by the inductance-capacity value of the circuit. 
This also will be explained later. The sets are easily de- 
signed to give any power required. Those in use range 
from a power of 2 kilowatts to 1,000 kilowatts. 
18 



274 RADIOTELEPHONY 

When a current passes continuously or nearly continu- 
ously through a small break in a circuit which is filled with 
air or other gas at atmospheric or greater pressure it is 
said to form an arc. This differs from a spark in that a 
spark is a disruptive discharge and the current passes 
only intermittently. A familiar example of an arc is the 
arc light used for lighting streets, etc. An arc has an un- 
usual feature in that it seemingly does not obey Ohm's 
law. It differs in the fact that it takes less voltage to 
cause a heavy current to pass across the arc than it does 
to cause a small current to pass. 

HOW THE ARC CIRCUIT WORKS. 

If capacity and inductance of proper value are shunted 
around the arc under proper conditions (shown by dashed 
lines in fig. 27), there will be radio-frequency oscillations 
produced in the circuit. These oscillations are produced 
because of the characteristics of the arc stated in the pre- 
ceding paragraph. This comes about as follows: Con- 
sider the circuit to the arc formed and fed from a constant 
current source and the condenser uncharged. The cur- 
rent feeding the arc will now also feed the condenser, thus 
charging it. 

But the current charging the condenser has been sub- 
tracted from the current passing through the arc, thus 
making the arc current less. The smaller arc current 
makes a higher voltage across the arc because of the arc 
characteristic mentioned. This higher voltage causes 
more current to pass into the condenser. This process 
goes on until the potential across the arc no longer rises 
rapidly with a decrease in current. Thus there is no 
higher potential available to charge the condenser, and 
hence part of the total current stops flowing into the con- 
denser and the total current now flows through the arc. 
This lowers the potential across the arc, and hence across 



MIRACLE OF THE AGE 



275 



the condenser. This lower potential allows the condenser 
to discharge and add its current to the feeding current of 
the arc. The inductance in the circuit causes the con- 
denser to be charged in the opposite direction. It imme- 
diately begins to discharge, and this time opposes the 
current flowing through the arc. These opposing cur- 
rents neutralize each other, whereupon the first condition 
is brought about. In good operation the back discharge 
of the condenser is great enough to stop the arc current 






FIG. 27. 



ATI 



I 




->-c> 



i 



T 
COPPER £ 

cazaza 



"vTJWQ^- 



__* 



from flowing. This extinguishes the arc, which, however, 
immediately re-forms. 

The frequency of the cycle described above can be 
varied by varying the inductance-capacity value of the 
shunt circuit around the arc. Thus the wave length may 
be changed. The oscillations are undamped because the 
source of current feeding the arc also supplies energy at 
each oscillation to the oscillating circuit, as has been de- 
scribed. 



276 KADIOTELEPHONY 

Figure 27 shows a diagram of such an arc set. The cir- 
cuit shows the conditions under which the arc will work. 
The first condition is that the arc must be between copper 
and carbon electrodes, the copper being the positive elec- 
trode and being kept cool by a stream of water. The car- 
bon must be slowly rotated around its own axis. The 
mechanical arrangement for doing this is not shown. The 
second condition is that the arc must be subject to a 
strong magnetic field. This magnetic field is furnished 
by the electromagnets EE. The third condition is that 
the arc is formed in a gas containing hydrogen. There- 
fore the arc is inclosed and this gas is furnished to the 
inclosure. In practice this can be done by dropping a 
few drops of alcohol in the arc container at regular in- 
tervals. This is accomplished by an arrangement similar 
to the oil dropper used on many machines. The fourth 
condition is that the value of the capacity and inductance 
of the shunt circuit must have a proper ratio. In the dia- 
gram of figure 27 the antenna is the condenser and the 
antenna tuning inductance, ATI, furnished the induc- 
tance. The dashed circuit shows the equivalent of these. 

METHODS OF CONTROLLING OUTPUT. 

Various arrangements of the key for controlling the 
output are possible. It has been found that the dots and 
dashes cannot be made by interrupting the source of con- 
stant current supply. This would extinguish the arc, 
which would have to be struck again by hand ; that is, by 
touching the carbon to the copper and then withdrawing 
it to make the arc. In the arrangement shown in figure 27 
the key cuts out some of the inductance in the antenna 
circuit. This changes the wave length radiated and the 
receiving antenna is not affected by this changed wave 
length, as it is tuned to the proper wave length. The key 



MIRACLE OF THE AGE 277 

is so arranged that when it is closed the proper inductance 
is in, and when it is open the inductance is changed from 
the proper value. Another method of controlling the out- 
put is by having a nonradiating circuit in addition to the 
antenna. Closing the key throws the output of the arc to 
this nonradiating circuit. Other methods are also used. 

RECEPTION OF UNDAMPED WAVES. 

The reception of damped waves has already been de- 
scribed. It was possible to receive them in that manner, 
because each signal (dot or dash) contained a number of 
wave trains and each wave train produced a vibration of 
the telephone diaphragm. The successive vibrations pro- 
duced by successive wave trains made the tone heard in 
the telephone receiver. As has been noted, an undamped 
wave signal is not broken up in wave trains but consists 
of an unbroken series of waves of the same amplitude. 
The effect upon the diaphragm of the telephone receiver 
would then be to distort it at the beginning of a signal and 
release it at the end of the signal. This would result in a 
click being heard in the receiver, but this would not be 
distinctive enough to be recognized. Therefore, some 
other method must be employed. 

A common method where only a crystal detector is used 
to receive undamped waves is by making use of an inter- 
rupter in the receiving circuit, as shown in figure 28-A. 
This is ordinarily a buzzer which is arranged to vibrate 
at suitable frequency. The vibration of the buzzer inter- 
rupts the circuit at P and thus breaks up into pulses the 
current flowing through the telephone. Each pulse pro- 
duces a vibration of the diaphragm and the successive 
pulses produce the note heard. 

Another method is by the use of the tikker. The circuit 
is shown in figure 28-B. The condenser, C, shunting the 



278 



RADIOTELEPHONY 



telephone receiver has a very large capacity compared to 
the variable condenser at C. The tikker is a specially de- 
signed interrupter. No detector is needed. The action 
of the tikker circuit is as follows: When the tikker 
' ' makes ' ' the circuit, only a very small part of the current 
passes through the telephone. Most of the current passes 




A F1&.2&. 



-L 







£t/zzer 



B 



<=_£ 



3 



Tikkeh 



into the condenser C, thus charging it. When the tikker 
opens the circuit, the charge condenser discharges 
through the telephone. As the condenser has a large ca- 
pacity, the discharge gives a current large enough to 
actuate the telephone diaphragm. A discharge occurs 
each time the tikker interrupts the circuit. This is at 
audio-frequency, so that a note is heard in the receiver. 
Other methods of receiving undamped waves will be dis- 
cussed under vacuum tubes. 



CHAPTER XXVII 

Now We Come to Vacuum Tube — Electric Action — The 

Batteries — Grid Action — Vacuum Tube as a Detector — 

As an Amplifier. 

WITHIN the past few years the vacuum tube is be- 
ing much used in radio communication. This de- 
vice is called various names, such as vacuum 
valve, special lamp, audion, ionic tube, thermionic tube, 
pliotron, and others. It will be called a vacuum tube in 
this volume. Vacuum tubes are used to generate un- 
damped radio waves ; to detect waves ; to amplify oscilla- 
tion both at radio and audio-frequencies; and in radio- 
telephony. They are very important and are gradually 
supplanting other radio apparatus because they are very 
light and portable, and because they are more efficient 
than other devices. 

A vacuum tube consists of a container, usually glass, 
from which the air has been pumped out. In this glass 
tube is mounted the filament, the grid, and the plate. 
Each of these elements is separated from the other by a 
space. The filament has two outlets, the grid one outlet, 
and the plate one outlet. The filament is surrounded by 
the grid, which in turn is surrounded by the plate. One 
type was illustrated in Chapter XXI. 

To understand the action of a vacuum tube it is neces- 
sary to remember the following facts : A current of elec- 
tricity is simply a flow of electrons, the electrons flow in 
one direction, which makes a current which is said to flow 
in the opposite direction. Electrons are small charges of 
negative electricity. All material contains electrons. 

279 



280 



RADIOTELEPHONY 



There are two kinds of electricity — positive and negative. 
Like electricity repels and unlike attracts. These facts 
are already known to the reader. The following addi- 
tional facts must be grasped before the action of the 
vacuum tube can be understood. It has been discovered 
that metals, if heated, will throw off into space some of 
the electrons which the metals contain. Also it has been 
discovered that the hotter the metal, up to a certain de- 
gree of heat, the more electrons it discharges. These 
electrons travel at a high rate of speed. If air or any 
other gas is present in the space around the metal, the 




Fig. 30. 




electrons strike the minute particles of the air or gas and 
are soon stopped. 

The facts stated above are applied in the vacuum tube. 
The air is pumped from the tube (hence the name vac- 
uum) so that the passage of the electrons will not be 
stopped. The filament, marked F in figure 30-A, is heated 
so that it becomes red or white hot. This is usually done 
by an electric current furnished by a battery. G repre- 
sents the grid and P the plate. These are represented in 
the method shown in figure 30 for ease of explanation. 
Suppose that the filament is hot and the grid and plate 
are not connected to outside circuits. The electrons are 
thrown off from the filament and strike both the grid and 
the plate. These acquire a negative charge, as they have 



MIRACLE OF THE AGE 281 

acquired electrons. The space inside the tube has also a 
negative charge as the space is filled with electrons. Like 
electricity repels and hence the negative charge on the 
plate, the negative charge on the grid, and the negatively 
charged space inside the tube are all repelling the elec- 
trons which the hot filament is trying to throw off. As 
each electron is thrown off of the filament it adds its 
charge, either to the plate, grid, or space. The stronger 
charge causes a stronger repulsion of the escaping elec- 
trons. In a very short while the repulsion is strong 
enough to prevent the escape of any more electrons from 
the filament. 

EFFECTS OF BATTERIES. 

Figure 30-B shows a battery, "A," used to heat the 
filament and a battery, "B," with its positive terminal 
connected to the plate and its negative terminal connected 
to the filament. The grid is shown connected to the plate, 
so that in effect it is a part of the plate. This is done for 
sake of clarity in explanation. The use of the grid will 
be shown later. By connecting the battery as shown in 
the figure, two things have been done. First, a positive 
potential has been placed on the plate ; second, a metallic 
circuit containing a battery has been made outside of the 
tube from the plate to the filament. This leaves only the 
space between the filament and the plate inside of the tube 
to complete the circuit. The battery marked A is used 
merely to heat the filament. 

The heated filament throws off electrons. The plate is 
positive and attracts the electrons which are negative. 
The electrons travel through the space (no air or gas par- 
ticles being present to hinder them as it is a vacuum) 
from the filament to the plate. Thus there is a flow of 
electrons from the filament to the plate — and a flow of 



282 RADIOTELEPHONY 

electrons is an electric current. Thus the combination 
of the heated filament, the vacuum, and the positively 
charged plate has caused a current to flow; that is, in 
effect, it has completed the circuit which contains the bat- 
tery, B. This complete circuit is (fig. 30-B) B a F P B. 

The action of the battery, B, is, as well known, com- 
parable to a pump. When it forms part of a circuit it 
pumps electrons out of its negative terminal and into its 
positive terminal. In the tube just described it pumps 
the electrons coming from the filament, from the plate to 
the battery and out of the battery to the filament. The 
filament again throws them off and they go to the plate — 
being attracted by it as it is positive. Thus the electrons 
flow around the circuit. This flow of electrons is a current 
of electricity. It can be measured by an ammeter placed 
at any convenient point in the circuit. 

BATTERY CONTROLS FLOW OF ELECTRONS. 

Consider the effect of changing the number of cells in 
the B battery. Changing the number of cells in the bat- 
tery would change the positive potential on the plate. If 
the positive potential on the plate became greater it would 
have a greater attraction for the flying electrons in the 
tube, and hence in a given time more electrons would ar- 
rive at the plate and be pumped around the circuit by the 
battery. An increased flow of electrons means an in- 
creased current. In the same way a decreased potential 
on the plate would cause a smaller current to flow. This 
change in current with a change in potential does not fol- 
low Ohm's Law. That is, doubling the potential does not 
double the current as it does in a wholly metallic circuit. 
Figure 31-A shows how the current varies with varying 
potential on the plate. Figure 31-B shows how the cur- 
rent varies with varying temperature of the filament. 



MIRACLE OF THE AGE 283 

In A the filament temperature has been kept at a con- 
stant value and by means of a milliameter the current 
passing through the plate circuit has been measured when 
the plate potential has a certain value. The value of the 
plate potential has then been changed and the plate cur- 
rent again measured. The curved line shows the result 
of a large number of these measurements. Note that a 
change of plate potential from value A to value B changes 
the current from value C to value D ; a change of poten- 
tial from value B to value E changes the plate current 
from value D to value F. In the case of this particular 
tube the exact figures are as follows: Raising the plate 
potential 20 volts, starting at 40 volts, increases the plate 
current 16 milliamperes ; raising the plate voltage 20 
volts, starting at 60 volts, increases the plate current only 
2 milliamperes. If the circuit obeyed Ohm's Law, the 
same change of potential would always produce the same 
change in current. 

EFFECT OF TEMPERATURE ON CURRENT FLOW. 

In figure 31-B, the plate voltage has been kept at a con- 
stant potential (85 volts) and the filament temperature 
varied. The plate current has been measured at each 
value of the filament temperature. The curve shows the 
result of a large number of measurements at different 
temperatures. It is seen that at a temperature of about 
1,800° (dull red glow) very little current flows. This 
means that at that temperature very few electrons are 
thrown off by the filament. From that point up to a tem- 
perature of about 2,050 (white hot) there is a rapid in- 
crease in the rate of emitting electrons with an increase 
in temperature, thus giving an increased current. An in- 
crease in temperature after this point has been reached 
does not increase the rate of emissions of the electrons. 



284 



RADIOTELEPHONY 




A 6 C 



PJate Voltage 



eor 



B 




e s vof+3 



BOO 1900 2000 2100 82.00 

FTtoment 7&mperotvr>e 



MIRACLE OF THE AGE 



285 



A current flows in the tube because the filament emits 
electrons. The electrons pass from the filament to the 
plate and grid. Neither the plate nor grid can emit elec- 
trons as they are not heated. This means that the elec- 
trons can pass only one way through the tube and hence 
an electric current can pass only one way through the 
tube. This is exactly what the galena crystal does. A 
vacuum tube with only a filament and plate (grid con- 




nected to the plate or not built in the tube) may be used as 
a detector in place of the galena crystal. Such a tube may 
also be used as a rectifier of alternating currents, because 
it allows current to pass only in one direction. The use of 
the grid greatly improves the action of the tube and will 
be explained before taking up the action of a vacuum tube 
used as a detector. 



ACTION OF THE GRID. 

As has been explained the plate current may be con- 
trolled by variation of the filament temperature and also 
by variation of the plate potential. It was discovered 
that putting a third element in the tube gives a more sen- 
sitive method of control. This third element is the grid 



286 KADIOTELEPHONY 

which has already been described. In the discussion 
above the grid has been connected with the plate, and 
hence really formed a part of the plate. In actual use it 
is in a different circuit from the plate. A study of figure 
32 will show the action of the grid. It must be remem- 
bered that the grid is of latticelike construction and is 
placed very near the filament and between the filament 
and the plate. 

The battery, C, allows a potential to be placed on the 
grid. This can be made stronger or weaker by changing 
the battery. It can be made positive or negative by re- 
versing the connection of the battery. Suppose a positive 
potential be placed on the grid. This attracts the elec- 
trons just as the positive potential on the plate did. Mak- 
ing the potential of the grid higher causes it to attract the 
electrons with more force, and thus causes a greater cur- 
rent to flow in the tube. The grid itself has a very small 
surface and does not catch many of the flying electrons. 
Most of the electrons therefore go past the grid and reach 
the plate. Thus the plate current is increased by an in- 
crease of potential on the grid. Putting a negative po- 
tential on the grid causes the grid to repel the electrons 
and thus decreases their rate of flow to the plate, as they 
cannot get through the grid. If this negative potential is 
made large enough, its repulsion of the electrons will en- 
tirely stop their flow and hence stop the passage of any 
current in the tube. Because of the nearness of the grid 
to the filament, a slight change in the potential on the grid 
makes a large change in current to the plate. The effect 
of changing the grid potential is much greater than ob- 
tained by changing the plate potential. 

It is important to understand this action of the grid, 
for upon it depends the use of the vacuum tube. The f ol- 



MIRACLE OF THE AGE 



287 



lowing mechanical device illustrates the action of a vac- 
uum tube. F, G, and P are all mounted in an inclosure 
from which most of the air has been pumped. The pipes 
are filled with flour — each particle of which represents an 
electron. A is a blower which is just strong enough to 
keep a fountain of flour, F in the diagram, in the space 
above its opening. A corresponds to the battery A in fig- 
ure 32, which heats the filament causing it to throw off 
electrons. B is a suction pump with a large funnel-like 
opening at P. B sucks the flour in at P and forces it 




through the pipe back to A. The pump B corresponds to 
the battery B in figure 32 ; the funnel P corresponds to 
the plate. It is evident that the stronger the suction at P, 
the more flour will be attracted. In the same way in the 
vacuum tube, the stronger the positive potential of the 
plate the more electrons will be attracted. If the pump B 
was reversed it would blow at P and no flour would enter, 
as it would be repelled. So in the vacuum tube, if the B 
battery is reversed it would put a negative potential on 
the plate and no current would flow, for the electrons 
would be repelled. 



288 



RADIOTELEPHONY 



The pump C corresponds to the battery C of figure 32. 
The inlet, G, corresponds to the grid of the vacuum tube. 
It consist of a large number of small openings connected 
to the pump. There is nothing between these openings so 
that the flour can pass directly from F to P without meet- 
ing any obstacles except at the openings themselves. 
With the pump B maintaining a uniform suction at P, let 
the pump C be started, starting a suction at G. G is much 
nearer to the fountain of flour than P and its effect is 
much greater. It sucks the flour towards it with great 







FlG&k 


so 








40 








l- 




f*$ 




5 20 
10 


If 


40 Volts on Plate 




"4 


Cs 





•50 



50 100 150 

Grid Voltage 



200 



250 



306 



speed. Most of the flour does not enter the openings of 
G as they are so small, but pass right by them and enter 
the funnel at P, thus increasing the amount entering P. 
In the same way placing a positive potential on the grid 
attracts the electrons and these fly past the grid to the 
plate. An increase of suction at C gives an increased flow 
of flour through P, in the same way as an increased po- 
tential on the grid causes an increased current of elec- 
tricity through the plate circuit. If the suction at C is 
made strong enough, however, the particles of flour are 
sucked with such force that, instead of flying past the 



MIRACLE OF THE AGE 



289 



openings at G, they are drawn from their straight path 
and made to enter them. They do not get to P and hence 
the flow to the plate is decreased. In the same way plac- 
ing too great a potential on the grid causes the electrons 
to fly to the grid instead of the plate, and hence the plate 
current is decreased at such high potential of the grid. 
Be versing the pump at C has the same effect of stopping 
the flow of flour as reversing the pump at B. If the pump 
C were reversed so that it acted as a blower it would tend 
to prevent any flour passing from F to P, as it would tend 




F/G.35. Plate Q grfrf 



300 Vo/t* on Plate 



Gr,J Current 




150 



zoo 



250 



300 



Grid Voltage 



to neutralize the effect of the pump B. The blower action 
would not have to be very strong to completely overcome 
the effect of the pump B. In the actual tube, giving the 
grid a negative potential has the same effect as making 
the pump, C, a blower. 

The actual change in current in the plate circuit due to 
change in potential on the grid is shown in figure 34 by 
the curve marked " Plate current." This was taken by 
measuring with a millimeter the amount of plate cur- 
rent passing when there was a definite voltage on the grid. 



290 RADIOTELEPHONY 

The grid voltage was changed and the plate current again 
measured. The curve shows the result of a large number 
of these measurements. The plate potential was kept 
constantly at 40 volts during the measurements. Note 
that the curve has two distinct bends, one at A and one at 
B. These bends are sometimes spoken of as the knees of 
the curve. It is to be noted that a rise of grid voltage 
starting at B does not make the same change of plate cur- 
rent as an equal lowering of grid voltage starting at the 
same point. The same fact holds for point A. 

In figure 34 the curve marked "Grid current' ' was ob- 
tained by taking a series of measurements of the value of 
the grid current with different values of the grid poten- 
tial. Note that when the grid potential becomes nearly 
equal in value to the plate potential (40 volts) the grid 
current rapidly rises, as it attracts the electrons so 
strongly that they go to the grid rather than the plate. 
Figure 35 shows the same series of measurements, except 
that the plate voltage was kept constantly at 300 volts. 

All the curves except that in 31 B are taken from actual 
measurements made on the same vacuum tube. This 
vacuum tube was designed to have 300 volts on the plate 
and to be used as a generator of oscillations in a manner 
to be explained later. It would not be efficient using 40 
volts on the plate, as the grid current is too large for small 
values of its potential. Some vacuum tubes are designed 
to have 40 volts on the plate and to have very small values 
of the grid current with this voltage. 

First method. — In this method a small condenser e, 
which is shunted by a very high resistance, r (about 
1,000,000 ohms), is inserted in the lead to the grid. The 
high resistance is called the grid leak. Figure 36 shows 
the circuits. Note that the circuits to the left of the ver- 
tical dashed line are exactly like the receiving circuits de- 



MIRACLE OF THE AGE 291 

scribed previously. The vacuum tube has the battery A 
(about 4 volts) to heat the filament. The plate battery, B, 
is connected through the telephone receivers to the plate. 
A variation in plate current therefore means a variation 
in the telephone current. There is no battery in the lead 
to the grid. The antenna is caused to oscillate by the in- 
coming signal waves. These oscillations are transferred 
to the secondary circuit. The terminal, d, of the con- 
denser is directly connected to the secondary circuit and 
hence it alternately becomes positive and negative. 

With no oscillation in the circuit the grid maintains a 
steady value, and therefore the plate current maintains a 
steady value. Let the oscillation begin and let the termi- 
nal, d, become positive. The positive electricity on that 
side of the condenser attracts the negative electricity to 
the other side and repels positive electricity so that "e" 
becomes negative and the grid becomes positive, or rather 
less negative than it was. This takes place because the 
' ' e ' ' side of the condenser and the grid are practically in- 
sulated from any other conductor — the grid leak has such 
a high resistance that no loss of electricity occurs through 
it in the short time taken by one oscillation — and any gain 
of electrons by the "e" side of the condenser must be 
compensated by an equal loss of electrons by the grid. 
Thus, as explained, the grid becomes positive (less nega- 
tive) when the "&" side of the condenser becomes posi- 
tive. The grid being positive now attracts the electrons 
coming from the filament and some of these electrons are 
added to the grid. These electrons are trapped on the grid 
and cannot escape. When the second half of the 
oscillations reaches d, d becomes negative, causing the 
grid side of the condenser to become positive and the grid 
itself to become negative. The grid being negative no 
electrons are added on this half of the oscillations. The 



292 



RADIOTELEPHONY 



net result of one complete oscillation is that the potential 
of the grid has been lowered, as electrons were added dur- 
ing the first half of the oscillation. Each succeeding oscil- 
lation adds its effect to the preceding one and hence the 
result of a complete wave train is to considerably reduce 
the potential of the grid. 





J H 
Grid Vo/+o$e 



The result of reducing the potential of the grid is to re- 
duce the plate current flowing in the valve. In figure 38 B, 
the steady potential (with no oscillations) is represented 
at H. This gives a steady value of the current repre- 
sented by the point K. The wave train reduces the grid 
potential to J which reduces the plate current and there- 



MIRACLE OF THE AGE 293 

fore the telephone current to L. Between each wave train 
there is sufficient time for the electrons on the grid to leak 
away through the grid leak. The grid therefore rises to 
its steady potential and hence the plate current rises to its 
steady value. 

The actual current is shown in figure 37. Each pulse of 
the current actuates the telephone diaphragm and hence 
a note is heard whose tone corresponds to the frequency 
of the received wave train. 

Second method. — In this method the knee of the plate 
current curve is used. The tube is connected as shown in 
figure 38 A. The sliding contact, P, on the resistance, E, 
allows the grid potential, which results from its being 
connected to the filament battery, to be adjusted so that 



Fig. 37. 

JteaSy Current 
Ware T*oin cYfecf Hbre Thorn effect 



its steady potential is at the knee of the curve. (A device 
allowing potential to be varied in this manner is called a 
potentiometer.) The variation of potential due to the 
oscillations set up in the oscillating current is communi- 
cated to the grid, whose potential therefore alternately 
rises and falls. 

Suppose the potentiometer has been adjusted so that 
the steady potential of the grid is at A (fig. 38 B). The 
oscillations cause the potential to rise to D and to fall to 
F ; the rise and the fall being equal to each other. When 
the grid has a steady potential at A, the steady plate cur- 
rent is represented by the point E ; when the first half of 
the alternation raises the grid potential to D, the plate 
current is increased to H; when the second half of the 



294 



RADIOTELEPHONY 



oscillation reduces the grid potential to F the plate cur- 
rent is reduced to G. It will be seen that the increase in 
current due to one half of the oscillation is much greater 
than the decrease due to the other half, for EH is much 
longer than EG and these two lengths measure the change 
in current. The result of this is that the current flowing 
through the telephone receiver is increased by an oscilla- 



Fig. 3Q. 





Grid Voltage 



tion. This increase of current lasts through one wave 
train, after which the current drops to its steady value. 
This is illustrated in figure 39. Each pulse actuates the 
telephone as previously described. In the explanation of 
both methods of detecting it is assumed that the telephone 
smooths out the pulsation that would otherwise occur at 
each oscillation. 



MIRACLE OF THE AGE 295 

It is possible by use of the vacuum tube to receive oscil- 
latory currents at one strength and send them out at a 
much higher strength. "When a tube is used for this pur- 
pose it is said to be used as an amplifier. The energy 
added by the use of the tube is furnished by the batteries 
connected to the tube. The amplification affected by one 
tube is considerable, in some cases the output energy of 
the tube being 100 times the input energy. 

A vacuum tube acts as an amplifier because, as has been 
noted, a small change of voltage on the grid makes a large 
change of current in the plate circuit. This is comparable 
to the fact that a small amount of pressure used by an 
engineer upon the throttle of a locomotive releases a large 
amount of pressure in the cylinders of the engine. 



Ft a. 33. 

Wave 7hrfo effect Wave Train Effect 



Jteody Current steady Current 



Figure 40 shows the type of connection necessary for 
use of a vacuum tube as an amplifier. This arrangement 
differs from that of a detector mainly in the fact that 
there is no grid condenser or grid leak, and the steady 
voltage of the grid is at neither the upper nor lower knee 
of the curve (fig. 38 B), but is between the two. It is to 
be noted that this part of the curve is practically straight. 
The oscillating circuit communicates its oscillating poten- 
tial to the grid. As the grid potential increases more 
electrons pass from the filament to the plate ; as the grid 
potential decreases fewer electrons pass from the filament 
to the plate. Thus the grid acts as a valve which turns on 
and off the current passing through the plate and fur- 
nished by the battery, B. The current oscillates with the 



296 



BADIOTELEPHONY 



same frequency as the grid potential, but carries much 
more energy than that acting upon the grid, because the 
battery, B, has added energy to the oscillation. 

A vacuum tube will amplify oscillations at any fre- 
quency, so that in radio apparatus some tubes are used to 
amplify radio frequency oscillations before they are de- 
tected, and some tubes are used to amplify oscillations 
after they have been acted upon by a detector and have 
been changed to audio frequency. The design of the cir- 
cuits for both radio-frequency and audio-frequency oscil- 



Fig.4-0. 




Oaeit/afion- 
Traiu 



Transform** 



« ' » Tb another 
^S ^amplifying tvH 



17 

T de- 



lations requires minute attention to details which are 
beyond the scope of this pamphlet. 

Tubes used as shown in figure 40 are said to be con- 
nected in cascade — the output of one tube being the input 
of another tube. This transfer of energy is usually made 
by means of an oscillation transformer having either an 
iron or an air core. The energy may be transferred by 
means of an electrostatic coupling which has been pre- 
viously described. Still another method much used in 
Europe is to have the output of one tube lead to the next 
tube through a high resistance. 



CHAPTER XXVIII. 

Vacuum Tube as a Generator of Undamped Oscillations 
— Summary of Radiotelephony — Receiving. 

VACUUM tubes may among other things be used to 
generate undamped waves. It has been noted that 
undamped waves are produced by adding energy 
to the oscillations at each oscillation. The batteries con- 
nected to a vacuum tube are the source of the energy when 
undamped waves are produced by the tube. A tube may 
be made to oscillate by coupling the grid and plate cir- 
cuits of the tube and having in each circuit the necessary 
capacity and inductance. Figure 41 is a simplified cir- 
cuit of a vacuum tube transmitter. B is a battery of 
320 volts. S and R are the coils of an oscillation trans- 
former. K is a key to control the oscillations. 

Before the key is closed the grid has a slight negative 
potential due to electrons from the filament being 
trapped on it. Therefore only a very small current is 
passing from the plate to the filament. Close the key 
and: 

(1) The grid acquires a zero potential (being con- 
nected to the ground) which 

(2) Increases the current in circuits B-R-F-P-B. 
(The grid, having a zero potential, does not prevent the 
passage of electrons through the tube.) The increasing 
of the current through coil, R, of the oscillation trans- 
former. 

(3) Builds up a potential in coil, S, so that the grid 
end of the coil and the grid itself become negative, which 

297 



298 



RADIOTELEPHONY 



(4) Decreases the current in circuit B-R-F-P-B. The 
decreasing of the current through coil, E, 

(5) Builds up a potential in coil, S, so that the grid 
end of the coil and the grid itself become strongly posi- 
tive, which 

(6) Greatly increases the current in circuit B-R-F-P- 
B, which is the beginning of another cycle. (See 2 above.) 




The oscillations are generated as long as the key is 
closed. It is to be noted that the oscillations have energy 
from the battery, B, added. Hence, they are undamped 
oscillations. The circuit containing the antenna deter- 
mines the frequency of the oscillations. The coupling 
between R and S must be close enough to cause the volt- 
age of the grid to vary over a range sufficient to keep the 
oscillations flowing in the circuit. 

Thus a vacuum tube will generate undamped waves 



MIRACLE OF THE AGE 299 

when the grid and plate circuits are coupled together. It 
is, of course, necessary that the degree of coupling be 
great enough for the reaction between grid and plate to 
continue as long as power is supplied or the coupling 
maintained. The circuits may be coupled by any means. 
A capacity coupling is often used, as is also a combined 
capacity and inductance coupling. 

REGENERATIVE AMPLIFICATION. 

It is possible to use the same vacuum tube as a detector 
and amplifier simultaneously. There are numberless 
methods of arranging the circuits of a tube and each 
different arrangement is designed to accomplish some 
object. A knowledge of the principles of radio circuits 
and the action of the tube itself, as heretofore described, 
will enable one to explain the action of any particular 
circuit. An example of an ingenious circuit is shown in 
figure 42. This is the same arrangement as shown in 
figure 36, where the tube was used as a detector, except 
that the coil, B, and the condenser, C, have been added. 

The coil R is coupled with the coil S, which is the sec- 
ondary of the oscillation transformer. When radio 
waves start oscillations in coil S, they are communicated 
to the grid as explained in connection with figure 36. The 
effect of the wave train upon the grid is to lower the 
potential of the grid as has been explained. The grid 
varies in potential with the radio frequency of the re- 
ceived oscillations. This radio-frequency variation in 
potential of the grid causes a radio-frequency variation 
of plate current strength (that is, an oscillation). This 
is in addition to the lowered potential produced by the 
wave train considered as a whole. Figure 42-B shows 
the combined results. The radio-frequency variation of 
potential in the grid superimposed upon the audio-fre- 



300 



KADIOTELEPHONY 



quency change in potential produces both a radio-fre- 
quency oscillation and an audio-frequency pulse in the 
plate circuit. The audio-frequency pulse gives rise to the 
tone heard in the receiver. The radio-frequency oscilla- 
tions, in passing through the coil, E, which is coupled to 
coil S, react upon coil S and strengthen the oscillations 
already existing in that coil. Thus the effect of the re- 
generative amplification is to strengthen the original os- 



Fig.IZ. 



§R 




lyWwJ 



vwvwA 6 




J 



B 






Wave Train Effect 



dilations and because of this strengthening make them 
persist longer than they otherwise would. 

The condenser, C, is used to allow the high frequency 
oscillations to by-pass both the receiver and the battery 
used. It offers a low resistance path to high frequencies 
while the high inductance of the receiver offers a high 
resistance to the high frequencies. It is a common prac- 
tice in radio to use a condenser for such a purpose. A 
condenser is oftentimes used in a circuit to permit alter- 



MIRACLE OF THE AGE 301 

nating currents to flow and at the same time to stop the 
passage of a direct current. In much the same way a 
large inductance is often used to stop the passage of high 
frequency variation in the current, as it offers a very 
high resistance to such oscillations. 

In addition to the methods of receiving undamped 
waves previously explained the heterodyne method is 
used. As this is the most sensitive method known it is 
gradually displacing all other methods. The word "heter- 
odyne" means "other force" (hetero — other; dyne — 
force). The name arises from the fact that besides the 
energy of the radio wave received by the antenna another 
radio wave is generated at the receiving station, and this 
wave adds its energy to the first one ; the second wave be- 
ing the "other force." 

The result of adding two waves together is the forma- 
tion of a wave which has the energy of each of the two 
waves which forms it. It is seen that if two waves having 
the same amplitude and the same frequency are added 
together, the result may be either the formation of a 
wave having double the amplitude of either one of the 
waves or the complete neutralization of the waves. The 
first result will be obtained when the two waves are in 
phase, i. e., when the crest of one coincides with the crest 
of the other. The second result will be obtained when 
the two waves are exactly opposite in phase, i. e., when 
the crest of one coincides with the trough of the other. 

Now, if we combine two waves of different frequencies, 
both conditions will be brought about, for if the crests 
coincide at one point they can not coincide at adjacent 
points because the waves have different frequencies and 
therefore have different wave lengths. The result is that 
the wave formed has varying amplitudes. These varia- 
tions in amplitude occur at regular intervals. Figure 43 



302 BADIOTELEPHONY 

shows the type of wave obtained. Notice that the wave 
varies from a large amplitude at L to a small amplitude 
at S and that this variation of amplitude repeats itself 
in a regular manner. These waves travel with the same 
velocity as ordinary waves. It has been found that the 
number of times per second the amplitude waxes and 
wanes when two waves are combined is equal to the dif- 
ference in frequencies of the two combined waves. Thus 
if a wave having a frequency of 350,000 is combined with 
a wave having a frequency of 351,000, the resulting wave 
will wax and wane 1,000 times per second (351,000 — 
350,000). The result of this waxing and waning of am- 
plitude is, after being acted upon by a detector, to give 
the effect of another wave shown by the dotted line in 
figure 43. This is sometimes called the beat wave and 
follows the variation in amplitude of the wave from 
which it results. This beat wave therefore has a fre- 
quency equal to the difference in frequencies of the two 
simple waves forming the varying amplitude wave. 

The oscillations set up in the receiving circuits have 
the same characteristics as the waves. The detector 
eliminates that part of the oscillation shown below the 
line, giving a pulsating direct current which is repre- 
sented by the dotted line in figure 43. This beat oscilla- 
tion is made to occur at audio frequency and hence can 
be heard when passing through the telephone receivers. 
The frequency of the beat oscillation is easily controlled. 
The antenna receives the wave sent out by the transmit- 
ting station. This has a definite frequency. The other 
wave is generated at the receiving station and its fre- 
quency may be changed at will. As explained, the differ- 
ence in the two frequencies determines the frequency of 
the beat wave and hence this latter can be made any fre- 
quency by varying the frequency of the local oscillation. 



MIRACLE OF THE AGE 



303 



The pitch of the note heard in the receivers depends up- 
on the number of beats, so that the pitch may be varied 
by varying the number of beats. 

The local oscillations are usually generated by a vacu- 
um tube. Figure 44 shows the circuits of an instrument 
used to generate such local oscillations. This instrument 
is usually called a heterodyne. Compare the circuits of 
figure 44 and figure 41, both of which are designed to 
generate oscillations. The main oscillating circuit is the 
circuit containing L and C, and the frequency of this cir- 
cuit determines the frequency of the oscillations. This 
frequency may be varied by the condenser, C. The grid 
circuit and the plate circuit react through the oscillation 
transformer composed of the coils L and P. The output 




oscillations are fed into the regular receiving circuits by 
means of a few turns, K, of the antenna lead-in wire, 
which make the coupling with the coil L. In many heter- 
odynes no special arrangements are made for coupling 
the heterodyne to the other circuits, as it is found that it 
is sufficiently simple to place the heterodyne near the 
other circuits. 

The practice of radiotelephony involves the elementary 
principles of radiotelegraphy previously described, and 
in addition new principles by which transmission of 
speech is made possible between radio stations. 



304 



EADIOTELEPHONY 



In ordinary wire telephony the sound waves produced 
by the voice are caused to produce, by means of a trans- 
mitter, a variation in a direct current; the variation in 
the current being identically similar in amplitude and 
frequency to the sound waves which produce it. This 
variation in direct current is usually converted, by means 
of a transformer, into a variation in alternating current 
which is similar to the variation in direct current. The 
variation in alternating current is then by means of a 
receiver converted into sound waves, the sound waves be- 
ing identically similar in amplitude and frequency to the 



g -< in series with Antenna Leatf-/n Wire 




* T 

i 



alternating current which causes them. As this identical 
similarity of amplitude and frequency has been main- 
tained throughout the complete cycle, the sound waves 
produced by the receiver are identical with those origin- 
ally produced by the voice. The series of events outlined 
above are represented by the curves of figure 45. 

The instruments peculiar to wire telephony are the 
transmitter and the receiver. The transmitter, some- 
times called a microphone, has two conductors separated 
by granules of carbon. The sound waves strike a flat 



MIRACLE OF THE AGE 



305 



piece of metal, called a diaphragm, and cause it to vibrate. 
The diaphragm acts upon the carbon granules, alter- 
nately increasing and decreasing the pressure of the 
granules upon one another, as it vibrates to-and-f ro. This 



« 


Fig. 45. 


Produced by Voice 


it 

i 


V ' Tim*. 


[y^. 


r\ r 


After betha, acf-eet 
\ upon by ThottemlHer 


j 


J WJ 


I yx> 


\S Time 


\~y 


c 


After being octet* 
V upon by Tre*t*to*nier 


1 


' 1 /*x *J 


1 f~\ S~\ 


w x„y 


L/^^ 


2 

1 





v /f fte f beitrg acted 
\ upon by receiver 


J* 


V— ~ Time. 









variation in pressure between the carbon granules varies 
the resistance of the granules. A direct current which 
is flowing through the granules is varied by this varying 
resistance. This varying direct current is changed into 
a varying alternating current by means of a step-up 
transformer. The alternating current acts upon the re- 
ceiver. This receiver consists of an electromagnet 
20 



306 



EADIOTELEPHONY 



through which the alternating current passes, and a per- 
manent magnet which forms the core of the electromag- 
net. Mounted in front of the poles of this combination 
magnet is a flat piece of metal containing iron. This is 
also called a diaphragm. The alternating current causes 
the diaphragm to vibrate, thus producing the sound made 
at the transmitter. 

In radiotelephony methods are employed to produce at 
the transmitter and reproduce at the receiver a sound 



Fig. 46. 
A 






i 


! 




B 




^^ Cbntitiut 


ws Wave 




, 


i 


i 








jpl 







wave, that is, a wave similar in character to that of figure 
45. It has been possible to do this by varying the ampli- 
tude of the radiated high-frequency waves so that this 
variation in amplitude follows in detail the wave varia- 
tion produced by the sound. In figure 46, curve A repre- 
sents a simple sound wave. By means of methods to be 
described later, the amplitude of a continuous radio wave 



MIRACLE OF THE AGE 



307 



is varied so that the variation in amplitude follows iden- 
tically the amplitude and frequency of the sound wave. 
This is shown by the heavy line in B of figure 46. This 
line, together with lower inclosing line, is called the 
envelop of the radio wave. Note that the upper and 
lower inclosing lines have the same shape. This wave 
establishes oscillations identical with it in the receiving 
antenna. When these oscillations are rectified by the 
detector and passed through a telephone receiver the 



FIG.4Q. 




7b source 
_ of Undamped 
O Haves 



n 



rectified current is similar to the heavy line of the en- 
velop. This is necessarily so as the rectified telephone 
current does not follow the change in each individual 
radio frequency oscillation, but follows the change in the 
amplitude of these oscillations. This change is repre- 
sented by one of the envelop lines as stated. 

When a radio wave has its amplitude varied so that its 
envelope is made to assume any desired curve the wave 
is said to be modulated. The instrument or apparatus 
that accomplishes this object is called a modulator. 

The simplest way of modulating a radio wave is by 
changing the resistance of the antenna. This change in 
resistance changes the intensity of high-frequency cur- 



308 



RADIOTELEPHONY 



rent in the antenna. This changes the amplitude of the 
oscillations as the amplitude varies with the intensity of 
current in the oscillation. Figure 48-A shows this simple 
arrangement where T is a microphone transmitter. 

Speech in the mouthpiece of the microphone varies the 
resistance of the aerial circuit, thus causing a variation 
in the current. A modification of this method is to have 
the microphone shunt a condenser in the antenna circuit 



Fig.4-3. 




30O Volts. 



20 vo/+f} 



7T 



Oscillations 'with 
200 Volts on P/afe 



^- 



Oscillation? with 
300 Volts on Plate 



or a part of the inductance in the circuit. By this method 
not only is the resistance varied but the antenna has its 
natural period of oscillation varied by the action of the 
microphone. This change in natural period throws the 
antenna circuit out of tune with its primary and hence 
changes the amount of current in it. This change in 
resonance can be made to add its effect to the change in 
resistance caused by the microphone. The methods of 
modulating described in this paragraph are not used 
very much because both of them waste a great deal of 
energy. 

Another method of modulation is called the absorption 
method. Figure 48-B is a schematic (simplified) diagram 



MIRACLE OF THE AGE 



309 



of the circuits. When the antenna is oscillating a part 
of its energy is absorbed by the circuit LT which is 
coupled to it. The amount of energy absorbed by this 
LT circuit depends upon its resistance. The resistance 
of this circuit is changed by the action of the microphone 
when its diaphragm is caused to vibrate by sound waves. 
The total energy in the antenna circuit is constant and 
hence any energy absorbed by the LT circuit is taken 
away from the radiated energy. Therefore the radiated 
energy is varied by the varying absorption of the circuit 
in which the microphone is placed. 



Receiver 



Fig. 51. 



TronstTtiftei* 



Leads 
Oscillograph 



iif 




4=® 



Referring to figure 31- A and its accompanying discus- 
sion, it is shown there that a variation of plate potential 
produces a variation in plate current. The following 
method of modulation depends upon that fact. In figure 
49 the line ABCD represents the characteristic curve of 
a vacuum tube with a plate potential of 300 volts ; the line 
EFG represents the characteristic curve of a vacuum 
tube with a plate potential of 200 volts. Start the tube 
oscillating when the plate potential is 200 volts. The 
oscillation would be as shown in the figure. Let the plate 
potential be increased to 300 volts. The oscillations then 
increase in amplitude as shown in the figure. 1 



310 



RADIOTELEPHONY 



The circuits for modulating a radio wave by means of 
varying the plate potential with a microphone are shown 
in figure 52. The coils marked R, F, C, are inductances 
of values large enough to prevent the passage of radio 
frequency oscillations. RFCi, prevents the oscillation 
from passing through the plate battery. The grid and 
filament are connected by the resistance, R, and the choke 
coil, RFC 2 . As the filament is connected to the negative 
terminal of the plate battery, the grid, being connected 
with the filament, acquires through the resistance, R, the 



Fig. 5Z. 




R.F.C.! 



Tel. Bottery 




proper negative potential at which it works efficiently. 
The choke coil in this circuit forces the oscillations to 
pass through the condenser, C, to which the filament is 
also connected. The condenser, C, assures the proper os- 
cillating voltage between the filament and the grid. The 
condenser C 2 , prevents the positive potential of the plate 
battery from reaching the grid through the coils of the 
autotransformer which couples the grid and the plate 
circuits. 

Speech into the microphone which is in circuit with a 
battery and the primary of a transformer varies the 



MIRACLE OF THE AGE 



311 



current passing through the circuit. This varying cur- 
rent in the primary induces a varying potential in the 
secondary. This varying potential in the secondary is 
impressed on the plate, thus varying the amplitude of the 
oscillations as has been explained. This arrangement is 
very simple but has the disadvantage of being limited in 
the amount of variation that can be produced in the plate 
potential. This limits the degree of modulation so that 
the set is not very effective. This method of modulation 
is very effective, however, when modified as explained 
below. 




Figure 53 is a simplified diagram of a complete radio- 
telephone set. LFC are inductances of such values as to 
choke out not only radio-frequency oscillations, but audio- 
frequency oscillations as well. They prevent the pass- 
age of audio-frequency oscillations or of audio-frequency 
variations in direct current through the circuit in which 
they are located. HPB! and HPB 2 are high-potential 
batteries feeding the plates of the vacuum tubes. T is a 
microphone, Tr is a step-up transformer. 

Speech into the microphone varies the current in its 
circuit. This varying current, passing through the pri- 
mary of the transformer, induces a varying Dotential in 



312 KADIOTELEPHONY 

the secondary. This varying potential in the secondary 
is impressed upon the grid of tube I. Tube I is a 
low-frequency amplifier. The plate current passing 
through tube I is therefore an amplified reproduction of 
the microphone circuit current. This current has audio- 
frequency variations in current which pass to the con- 
denser K and through the condenser to the grid of tube 
II. They can not take any other path as the low-fre- 
quency choke coil in other paths reject them. The con- 
denser K is in the circuit to prevent the current and posi- 
tive of HPB 2 from reaching the grid of Tube II. By ac- 
tion of the condenser K, the low-frequency variations of 
the direct current reaching it from the plate circuit, tube 
I, are changed into low-frequency alternating current, 
which is the current that reaches the grid of tube II. 

Tube III generates continuous oscillations (compare 
with fig. 52) . Its plate is connected with the plate of tube 
II . The high-potential battery, HPBx, feeds both the 
plate of tube II and the plate of tube III. It furnishes a 
constant current because it has a low-frequency choke 
coil in series with it and this choke coil prevents any 
variation in current that takes place in either of its 
branch circuits from affecting the battery. As noted in 
connection with figure 52, the high-frequency choke coil, 
EFCi, stops all radio oscillation in its circuit. 

No radio-frequency oscillation, therefore, can reach the 
plate of tube II. The audio-frequency variation in the 
potential of the grid of tube II produces an audio-fre- 
quency variation of current in the plate circuit. This 
variation of current can not come directly from the bat- 
tery, as the low-frequency choke coil prevents; it must 
come from tube III. When the current in tube II is in- 
creased, the current in tube III is decreased; when the 
current in tube II is decreased, the current in tube III is 



MIRACLE OF THE AGE 313 

increased. Thus the amplitude of oscillation in tube III is 
modulated by this increase and decrease of current. It is 
the output of tube III which is radiated by the antenna. 
Figure 54 illustrates the transfer of energy between 
tubes II and III. The battery, B, furnishes a constant 
current passing through K. This current divides, half of 
it going through tube A and half of it through tube D 
when both have the same resistance. If the resistance of 
D is decreased, more current will flow through it. But 
K does not allow any variation in current, therefore the 
extra current passing through D must come from the 
circuit in which A is located. In other words, the cur- 




rent passing through K does not split 50-50, but, say, 
80-20, the larger part going through the D circuit. When 
the resistance of D is increased the reverse of this takes 
place, the larger current passing through A. A and D 
represent the tubes and K represents the low-frequency 
choke coil of figure 52. The varying potential on the 
grid of tube II has the effect of changing the resistance 
of that tube. 

A variation of the above method is to make the sum of 
the potential of the plates of tubes II and III constant, 
instead of having the sum of their currents constant. 
This is done by replacing LFd (fig. 53) by a transfor- 
mer, as shown in figure 55. This transformer has a ratio 



314 EADIOTELEPHONY 

of 1 to 1 ; that is, the voltage produced in the secondary 
is the same as the voltage in the primary. A variation 
in the current passing through the plate of tube II takes 
a path through the primary of the transformer and 
through the battery. The transformer is so arranged 
that an increase of current through P reacts through the 
transformer to produce a decrease in voltage at the plate 
end of the secondary. An increase or decrease in poten- 
tial of the plate of tube II is therefore compensated by 
an equal decrease or increase in potential of the plate of 
tube III. 




A radiotelephone transmitting set is readily adapted 
to send telegraphic signals by means of the buzzer modu- 
lator method. An ordinary buzzer replaces the telephone 
transmitter. The buzzer, by making and breaking the 
circuit, modulates the output of the transmitter in much 
the same way as is done by a microphone. The effect is 
to chop up the output into groups of waves, each succeed- 
ing group differing in amplitude from the preceding one 
but each alternate group having the same amplitude. As 
there are a number of such groups in the time it takes to 
make a dot or dash, such transmission can be received 
by any method suitable to damped wave radiotelegraphy. 



THE RADIO DICTIONARY 

Aerial — The wires or wire by or which the electric energy 
is radiated into the ether in transmission, or through 
which the waves motions are felt and carried into the 
receiver. 

Alternating Current — A current of electricity which 
changes its flow of direction at regular alternating 
periods. It flows first in one direction and then in 
the opposite. One complete alternation is called a 
"Cycle." 

Amplifier — A term used to describe any device which in- 
creases or adds energy to an incoming wave. It may 
be an electron tube or an amplifying unit. 

Amplitude — The maximum value of a wave is its ampli- 
tude. This is determined by measuring the height of 
the wave crest. Every wave increases from zero up- 
ward to the maximum, just as waves on the ocean 
have their lowest and highest points. 

Ampere — The unit of measurement in electricity used to 
describe and determine the strength of a current. 

Antenna — The correct name of the receiving or transmis- 
sion wires frequently called aerial. In later day 
radio sets the antenna is not necessarily "up in the 
air" in the sense that it was when aerial was first 
used to describe it. 

Audibility — The measure of strength of an incoming 
signal. 

Audion — The trade name of a vacuum or electron tube. 
It is an incandescent bulb containing the filament, a 
metal plate and a grid, or wire screen, which is at- 
tached to a battery. It is variously called vacuum 

315 



316 BADIOTELEPHONY 

tube, thermionic valve, oscillating valve and electron 
tube. It can act as a generator of waves, an ampli- 
fier and a detector. 

Battery — A device for holding in reserve and exerting 
through chemical action, electrical energy. It con- 
sists of a series of perforated lead-plates, each one 
insulated from its neighbor. Half the plates are 
positive. The other half negative. They are con- 
nected as a unit but arranged alternately — first a 
positive and then a negative plate. Over and be- 
tween the plates is a fluid called " electrolyte ' ! con- 
sisting 'of sulphuric acid and pure water, usually in 
parts of about one to four. When the battery is 
charged with electricity a chemical action takes place 
and small particles of lead are taken up from one 
plate and carried to the other, thus converting elec- 
trical energy. 

"B" Battery — A dry cell battery used to supply current 
to the grid in a vacuum tube. Has high voltage run- 
ning from 15 to 22 volts, but with low amperage. 

Broadcasting — The sending of telephone or telegraph 
communications, messages, concerts or speeches 
through the ether so that they may be picked up by 
any number of stations simultaneously. 

Capacity — A term used principally with relation to con- 
densers. It refers to the amount of energy which a 
condenser will store up. 

Cascade Amplification — A system of amplifying received 
radio signals whereby the sounds or waves pass 
through vacuum tubes one after another. 

Cat's whisker — A term used to describe the fine wire con- 
tact point on a crystal detector. So called because it 
looks like a "cat whisker." 



MIEACLE OF THE AGE 317 

Circuit — A complete metal path used for conveying an 
electric current — the course covered by a current 
from its source of origin back to its original source. 

Close-coupling — Eefers to the method of mounting a pri- 
mary and secondary tuning coil to cause inductance. 
When the coils are close together they are "close- 
coupled." 

Condenser — A device for storing up electrical energy. 
It consists of alternating layers of conductors and 
nonconductors and in radio is used for collecting 
energy and for bringing circuits into resonance so 
as to tune them. 

Counterpoise — A series of wires placed at the ground 
directly beneath the antenna — sometimes buried — to 
insure better ground connection. Frequently it is in 
replica of the antenna above it. 

Crystal Detector — A device used to rectify radio fre- 
quency currents to direct impulses which effect the 
diaphram of the receiver. 

C. W. — Continuous Waves. 

Detector — A device which transforms the electrical vi- 
brations set up in the aerial or antenna into visible 
or audible vibrations. 

Direct Current — A current of electricity which flows in 
one constant direction. The alternating current 
alters or reverses its direction. 

Electron — The electric atom — the elementary corpuscle 
of electricity. 

E. M. F. — The sign used to indicate electromotive force in 
electricity. The unit of E. M. F. is the volt. 

Ether — A compressible substance that is supposed to fill 
the space between all molecules of material through- 
out the universe, whether it be water, gas, air or what 
to us are "hard" substances. It is the medium 



318 RADIOTELEPHONY 

through which radio messages are transmitted. They 
are carried on ether waves. 

Frequency — A term used to indicate the number of oscil- 
lations a second which an alternating current makes. 

Grid — The small wire screen placed between the film and 
the plate in a vacuum tube, and which serves as con- 
trol of the electric energy which passes from the 
heated film to the plate. The discovery of its power 
and influence made possible the really efficient wire- 
less telephone. 

Ground — The term used to designate a connection made 
to the earth, river or sea in completing an electrical 
circuit. 

Harmonics — A secondary or overtone — usually several 
degrees higher than the original vibration. In music 
they are familiar to nearly every one. They are vi- 
brations of greater intensity than the fundamental 
vibrations and are clear and bell like. They are fre- 
quently annoying in radio operation. 

Henry — The name given to the unit of inductance. 

Hertzian Waves — The electromagnetic waves in the 
ether named after the man who discovered their ex- 
istence, or rather who proved they existed. 

Hook-up — A term used in describing the system of mak- 
ing up the circuit of radio set. By common practice 
applied to diagrams showing the " hook-ups.' ' 

Impedence — A term used to describe a form of resistance 
offered to the flow of a current by a wire on account 
of back electromotive force. 

Inductance — A term used to designate that phenomena by 
which a current from an electrified wire or body can 
be made to flow in an adjacent wire when there is no 
actual contact between the wires. 



MIRACLE OF THE AGE 319 

Lead-in — The wire connecting the antenna with the re- 
ceiving set in radio. 

Loop — Loop-antenna — A small frame around which 
wires are stretched and which is sensitive to the ether 
waves. It is used in place of outside overhead 
straight wire aerials or antenna. 

Loud Speaker — A device used to magnify the received 
messages or signals so that they can be heard with- 
out resort to telephone head pieces. 

Nagative Pole — The side of an electric circuit opposite 
to the positive and indicated by the minus sign ( — ). 
It is the side surcharged by electrons, and from 
which they flow to the positive. 

Meter — A unit of distance equal to 39.37 inches. A unit 
of the metrical system of measurement universally 
used in scientific work. 

Microphone — A sensitive type of telephone transmitter. 

Mfd — An abbreviation used to designate the Microfarad 
— the one-millionth part of a Farad, and the practical 
unit of capacity. 

Positive Pole — The side of a circuit indicated by the plus 
sign (+). The side with a deficiency of electrons 
and to which they flow from the negative side. 

Radio Frequency — An arbitrary term used to indicate 
frequencies that are beyond the range of audibility. 
In radio all frequencies that are beyond about 10,000 
per second are above audibility — so rapid they can- 
not be detected normally. 

Rectifier — A device which suppresses one of the impulses 
of an alternating current, so that it is actually trans- 
formed into a current consisting of a series of spurts 
in one direction. That this could be done was one of 
the essential discoveries of radio. 



320 



RADIOTELEPHONY 



Resistance— The opposition offered to the flow of a cur- 
rent. 

Rheostat — A variable resistance used to regulate the flow 
of electric current. 

Selectivity — The ability to choose any wave length to the 
exclusion of all other waves lengths in receiving. 

Static — Natural electric discharges or interference by the 
elements of nature which are heard in radio receiving 
and which are the bane of all radio operators. 

Transformer — A device used to change electric energy 
from one state to another — either from alternating 
to direct or direct to alternating under varying condi- 
tions. 

Vacuum Tube — The electron tube consisting of incan- 
descent bulb with film, grid and plate already de- 
scribed. See Audion. 

Volt — The unit of electrical pressure. 

Wave Length — The distance from the crest of one ether \ 
wave to another, which is always computed in meters. ) 




